Welding electrode cutting tool and method of using the same

ABSTRACT

A cutting tool that can simultaneously cut and restore asymmetric weld face geometries of two welding electrodes that are subject to different degradation mechanisms is disclosed along with a method of using such a cutting tool during resistance spot welding of workpiece stack-ups that include dissimilar metal workpieces. The cutting tool includes a first cutting socket and a second cutting socket. The first cutting socket is defined by one or more first shearing surfaces and the second cutting is defined by one or more second shearing surfaces. The first shearing surface(s) and the second shearing surface(s) are profiled to cut and restore a first weld face geometry and a second weld face geometry, respectively, that are different from each other upon receipt of electrode weld faces within the cutting sockets and rotation of the cutting tool.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit of U.S. Provisional Application No.62/291,030, which was filed on Feb. 4, 2016. The aforementionedprovisional application is incorporated herein by reference in itsentirety.

TECHNICAL FIELD

The technical field of this disclosure relates generally to a cuttingtool for dressing welding electrodes that are used to resistance spotweld workpiece stack-ups that include dissimilar workpieces such as analuminum workpiece and an adjacent steel workpiece.

BACKGROUND

Resistance spot welding is a process used by a number of industries tojoin together two or more metal workpieces. The automotive industry, forexample, often uses resistance spot welding to join together metalworkpieces during the manufacture of structural frame members (e.g.,body sides and cross members) and vehicle closure members (e.g., vehicledoors, hoods, trunk lids, and lift-gates), among others. A number ofspot welds are often formed at various points around an edge of themetal workpieces or some other bonding region to ensure the part isstructurally sound. While spot welding has typically been practiced tojoin together certain similarly composed metal workpieces—such assteel-to-steel and aluminum-to-aluminum—the desire to incorporatelighter weight materials into a vehicle body structure has generatedinterest in joining steel workpieces to aluminum workpieces byresistance spot welding. The aforementioned desire to resistance spotweld dissimilar metal workpieces is not unique to the automotiveindustry; indeed, it extends to other industries that may utilize spotwelding including the aviation, maritime, railway, and buildingconstruction industries.

Resistance spot welding, in general, relies on the flow of electricalcurrent through overlapping metal workpieces to generate heat within thedesignated weld site. To carry out such a welding process, a set ofopposed welding electrodes is pressed in facial alignment againstopposite sides of the workpiece stack-up, which typically includes twoor three metal workpieces arranged in a lapped configuration. Electricalcurrent is then passed through the metal workpieces from one weldingelectrode to the other. Resistance to the flow of this electricalcurrent generates heat within the metal workpieces and at their fayinginterface(s). When the workpiece stack-up includes an aluminum workpieceand an adjacent overlapping steel workpiece, the heat generated at thefaying interface and within the bulk material of those dissimilar metalworkpieces initiates and grows a molten aluminum weld pool that extendsinto the aluminum workpiece from the faying interface. This moltenaluminum weld pool wets the adjacent faying surface of the steelworkpiece and, upon cessation of the current flow, solidifies into aweld joint that weld bonds the two workpieces together.

Each of the welding electrodes used to conduct resistance spot weldingincludes a weld face disposed on an end of an electrode body. The weldface is the portion of the welding electrode that contacts andelectrically communicates with the workpiece stack-up. Over the courseof repeated resistance spot welding operations, the weld faces of thewelding electrodes are susceptible to degradation due to the largequantity of heat generated at the weld faces during current flow and thehigh compressive force used to hold the weld faces against the workpiecestack-up. Such degradation may include plastic deformation of the weldface and/or contamination build-up that results from a reaction betweenthe electrode and its respective contacting workpiece at elevatedtemperatures. In order to extend the life of the welding electrodes,especially in a manufacturing setting, the weld faces of the weldingelectrodes may be periodically restored to their original geometry. Thisrestorative process should be quick, practical, and accurate so that itdoes not disrupt manufacturing operations by keeping the weldingelectrodes off-line for extended periods of time.

Resistance spot welding an aluminum workpiece to a steel workpiece isfraught with challenges. Apart from the need to periodically dress weldfaces that undergo different degradation mechanisms, the disparateproperties of the two workpieces and the presence of a mechanicallytough, electrically insulating, and self-healing refractory oxide layer(or layers) on the aluminum workpiece have made it difficult toconsistently achieve weld joints with adequate peel and cross-tensionstrengths. Given that previous spot welding efforts have not beenparticularly successful, mechanical fasteners including self-piercingrivets and flow-drill screws have predominantly been used to fastenaluminum and steel workpieces together. Mechanical fasteners, however,take longer to install and have high consumable costs compared to spotwelding. They also add weight to the vehicle body structure—weight thatis avoided when joining is accomplished by way of spot welding—thatoffsets some of the weight savings attained through the use of aluminumworkpieces in the first place. Additionally, mechanical fasteners canintroduce locations for galvanic corrosion with the aluminum workpiecesince the fasteners are typically made of steel.

SUMMARY OF THE DISCLOSURE

One embodiment of a cutting tool capable of dressing asymmetric weldface geometries of first and second welding electrodes includes a bodyand a cutting member within the body. The body has a first end having afirst opening and a second end having a second opening. The cuttingmember has one or more cutting flutes. Each of the one or more cuttingflutes extends inwardly from an interior surface of the body andcomprises a cutting blade that has axially spaced apart and opposedfirst and second shearing surfaces. The one or more cutting flutes thusestablish a first cutting socket, which is defined by the first shearingsurfaces(s) and accessible through the first opening of the body, and asecond cutting socket, which is defined by the second shearingsurface(s) and accessible through the second opening of the body. Thefirst cutting socket is constructed to cut a first weld face geometryinto a weld face of a first welding electrode and the second cuttingsocket is constructed to cut a second weld face geometry into a weldface of a second welding electrode when the weld faces of the first andsecond welding electrodes are received in the first and second cuttingsockets, respectively, and the cutting tool is rotated. The first weldface geometry and the second weld face geometry are different from oneanother.

The construction of the cutting tool is subject to some variabilitywithout losing its dressing capability. For example, each of the one ormore cutting flutes may comprise an elongate foot that supports thecutting blade at the interior surface of the body. The elongate foot ofeach of the one or more cutting flutes may be friction fit within aretention channel defined by a depressed surface in the interior surfaceof the body to fixedly retain the cutting member within the body. Or, inanother implementation, the elongate foot of each of the one or morecutting flutes may be integrally formed with the interior surface of thebody to fixedly retain the cutting member within the body.

As another example of a specific construction of the cutting tool, thecutting member may comprise a first cutting flute having a first cuttingblade, a second cutting flute having a second cutting blade, a thirdcutting flute having a third cutting blade, and a fourth cutting flutehaving a fourth cutting blade. The first, second, third, and fourthcutting blades are circumferentially spaced from each other such thateach of the first, second, third, and fourth cutting blades is orientedtransverse to each of its two circumferentially adjacent cutting blades.Additionally, each of the first, second, third, and fourth cuttingblades includes axially spaced apart and opposed first and secondshearing surfaces. The first shearing surfaces of the first, second,third, and fourth cutting blades define the first cutting socket and thesecond shearing surfaces of the first, second, third, and fourth cuttingblades define the second cutting socket.

Still further, when the cutting member includes the first, second,third, and fourth cutting blades, each of the first shearing surface ofthe first cutting blade and the first shearing surface of the thirdcutting blade, which are aligned, has a lower end portion having anupwardly profiled leading edge and an upwardly profiled trailing edgethat is offset below the leading edge by a positive relief angle.Similarly, each of the second shearing surface of the second cuttingblade and the second shearing surface of the fourth cutting blade, whichare aligned yet oriented transverse to the first shearing surface of thefirst cutting blade and the first shearing surface of the third cuttingblade, has a lower end portion having an upwardly profiled leading edgeand an upwardly profiled trailing edge that is offset below the leadingedge by a positive relief angle.

The first and second shearing surfaces of the first, second, third, andfourth cutting blades may have additional structure besides theirrespective lower end portions. For instance, the first shearing surfaceof each of the first, second, third, and fourth cutting blades may alsoinclude an upper end portion that is convex in shape. The upper endportion of the first shearing surface of each of the first, second,third, and fourth cutting blades has a leading edge and a trailing edge.Likewise, the second shearing surface of each of the first, second,third, and fourth cutting blades may include an upper end portion thatis convex in shape. The upper end portion of the second shearing surfaceof each of the first, second, third, and fourth cutting blades has aleading edge and a trailing edge.

As yet another example of a specific construction of the cutting tool,the body of the cutting tool may comprise an annular wall having anexterior surface that includes an integral retaining nut that has aplurality of planar surfaces arranged around the exterior surface andwhich intersect at circumferentially spaced axial edges. The body of thecutting tool, moreover, may further include an integral radial flangethat adjoins and bears on an axial end of the integral retaining nut toprovide a semicircular seating surface that projects transversely fromeach of the planar surfaces of the integral retaining nut. Otherconstructions and variances of the body of the cutting tool may ofcourse be employed to both support the cutting member and to enable tothe cutting tool to be received and clutched within a rotating cuttingtool holder.

Another embodiment of a cutting tool capable of dressing asymmetric weldface geometries of first and second welding electrodes includes a bodyand a cutting member within the body. The body extends longitudinallyalong a central axis between a first end and a second end. The cuttingmember establishes a first cutting socket accessible through the firstopening at the first end of the body and further establishes a secondcutting socket accessible through a second opening at the second end ofthe body. The cutting member comprises a cutting flute that includes acutting blade having axially spaced apart and opposed first and secondshearing surfaces that define, at least in part, the first and secondcutting sockets, respectively. The first shearing surface comprises alower end portion profiled to cut a first weld face geometry and thesecond shearing surface comprises a lower end portion profiled to cut asecond weld face geometry that is different from the first weld facegeometry.

The first and second weld face geometries that are dressable by thecutting tool encompasses many different combinations. For instance, inone embodiment, the first weld face geometry comprises a planar or domedbase weld face surface that has a diameter between 3 mm and 16 mm, andthe second weld face geometry comprises a domed base weld face surfacethat has a diameter between 8 mm and 20 mm and further includes acentral plateau centered on the domed base weld face surface. In anotherexample, the first weld face geometry comprises a planar or domed baseweld face surface that has a diameter between 3 mm and 16 mm, and thesecond weld face geometry comprises a domed base weld face surface thathas a diameter between 8 mm and 20 mm and further includes a centralplateau centered on the domed base weld face surface and a plurality ofterraces that surround the central plateau.

In still another example, the first weld face geometry comprises a domedbase weld face surface that has a diameter between 8 mm and 20 mm andfurther includes a central plateau centered on the domed base weld facesurface, and the second weld face geometry comprises a domed base weldface surface having a diameter between 8 mm and 20 mm and a series ofupstanding circular ridges that project outwardly from the domed baseweld face surface. The series of upstanding circular ridges may includeanywhere from two to ten upstanding circular ridges that increase indiameter from an innermost upstanding circular ridge to an outermostupstanding circular ridge. The upstanding circular ridges may be spacedapart on the domed base weld face surface by a distance of 50 μm to 1800μm while each of the ridges has a ridge height that ranges from 20 μm to500 μm. And in yet another example, the first weld face geometrycomprises a domed base weld face surface that has a diameter between 8mm and 20 mm and further includes a central plateau centered on thedomed base weld face surface, and the second weld face geometrycomprises a domed base weld face surface that has a diameter between 8mm and 20 mm and further includes a central plateau centered on thedomed base weld face surface and a plurality of terraces that surroundthe central plateau.

The construction of the cutting tool is subject to some variabilitywithout losing its dressing capability. For example, the cutting membermay comprise a first cutting flute having a first cutting blade, asecond cutting flute having a second cutting blade, a third cuttingflute having a third cutting blade, and a fourth cutting flute having afourth cutting blade. The first, second, third, and fourth cuttingblades are circumferentially spaced from each other such that each ofthe first, second, third, and fourth cutting blades is orientedtransverse to each of its two circumferentially adjacent cutting blades.Additionally, each of the first, second, third, and fourth cuttingblades includes axially spaced apart and opposed first and secondshearing surfaces. The first shearing surfaces of the first, second,third, and fourth cutting blades define the first cutting socket and thesecond shearing surfaces of the first, second, third, and fourth cuttingblades define the second cutting socket.

Still further, when the cutting member includes the first, second,third, and fourth cutting blades, each of the first shearing surface ofthe first cutting blade and the first shearing surface of the thirdcutting blade, which are aligned, has a lower end portion having anupwardly profiled leading edge and an upwardly profiled trailing edgethat is offset below the leading edge by a positive relief angle.Similarly, each of the second shearing surface of the second cuttingblade and the second shearing surface of the fourth cutting blade, whichare aligned yet oriented transverse to the first shearing surface of thefirst cutting blade and the first shearing surface of the third cuttingblade, has a lower end portion having an upwardly profiled leading edgeand an upwardly profiled trailing edge that is offset below the leadingedge by a positive relief angle.

A method of dressing welding electrodes having asymmetric weld facegeometries includes several steps according to one embodiment of thedisclosure. In particular, a cutting tool is provided that includes abody and a cutting member within the body. The cutting member comprisesone or more cutting flutes that establish a first cutting socket and asecond cutting socket. The first cutting socket is accessible through afirst opening at a first end of the body and the second cutting socketis accessible through a second opening at a second end of the body. Afirst weld face of a first welding electrode is received in the firstcutting socket and a second weld face of a second welding electrode isreceived in the second cutting socket. Once the first and second weldfaces are received in the first and second cutting sockets,respectively, the cutting tool is rotated to cut and restore a firstweld face geometry in the first weld face and a second weld facegeometry in the second weld face. The first weld face geometry isdifferent from the second weld face geometry.

The method of dressing welding electrodes having asymmetric weld facegeometries may be practiced with certain preferences. For instance, thecutting tool may be rotated between one and ten full rotations aboutaxes of the first and second weld faces such that a depth of materialranging from 10 μm and 500 μm is removed from each of the first weldface and the second weld face during restoration of the first weld facegeometry and the second weld face geometry. Additionally, a set of tento one hundred weld joints between overlapping and adjacent steel andaluminum workpieces may be formed prior to receiving the first weld facein the first cutting socket of the cutting tool and the second weld facein the second cutting socket of the cutting tool. Many other variationsof the resistance spot welding method may of course be practiced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a cutting tool according to oneembodiment of the present disclosure, and, in particular, the firstcutting socket of the cutting tool;

FIG. 2 is a perspective view of the cutting tool depicted in FIG. 1,and, in particular, the second cutting socket of the cutting tool;

FIG. 3 is an exploded view of the cutting tool depicted in FIGS. 1-2showing a body and a cutting member separated from one another accordingto one embodiment of the disclosure;

FIG. 4 is a cross-sectional view of the cutting tool depicted in FIGS.1-2 according to one embodiment of the disclosure;

FIG. 5 is a plan view of the first cutting socket of the cutting tooldepicted in FIGS. 1-2 according to one embodiment of the disclosure;

FIG. 6 is a plan view of the second cutting socket of the cutting tooldepicted in FIGS. 1-2 according to one embodiment of the disclosure;

FIG. 7 is a cross-sectional view of a blade portion of one of thecutting flutes taken along section lines 7-7 in FIG. 5;

FIG. 8 is a cross-sectional view of a blade portion of one of thecutting flutes taken along section lines 8-8 in FIG. 6;

FIG. 9 is a general perspective view of a welding electrode thatincludes a first weld face geometry according to one embodiment of thedisclosure;

FIG. 10 is a general perspective view of a welding electrode thatincludes a second weld face geometry, which is different from the firstweld face geometry shown in FIG. 9, according to one embodiment of thedisclosure;

FIG. 11 is a general perspective view of another welding electrode thatincludes a first weld face geometry according to one embodiment of thedisclosure;

FIG. 12 is a general perspective view of another welding electrode thatincludes a second weld face geometry, which is different from the firstweld face geometry shown in FIG. 11, according to one embodiment of thedisclosure;

FIG. 13 is a general perspective view of yet another welding electrodethat includes a first weld face geometry according to one embodiment ofthe disclosure;

FIG. 14 is a general perspective view of yet another welding electrodethat includes a second weld face geometry, which is different from thefirst weld face geometry shown in FIG. 13, according to one embodimentof the disclosure;

FIG. 15 is a magnified cross-sectional view of the weld face of thewelding electrode shown in FIG. 14;

FIG. 16 is a general perspective view of still another welding electrodethat includes a first weld face geometry according to one embodiment ofthe disclosure;

FIG. 17 is a general perspective view of still another welding electrodethat includes a second weld face geometry, which is different from thefirst weld face geometry shown in FIG. 16, according to one embodimentof the disclosure;

FIG. 18 is a general cross-sectional view of a workpiece stack-up, whichincludes a steel workpiece and an adjacent aluminum workpiece assembledin overlapping fashion, situated between a first welding electrode and asecond welding electrode in which the first and second weldingelectrodes have different weld face geometries;

FIG. 27 schematically depicts a further embodiment.

FIG. 19 is a general cross-sectional view of a workpiece stack-up, whichincludes a steel workpiece and an adjacent aluminum workpiece assembledin overlapping fashion, situated between a first welding electrode and asecond welding electrode in which the first and second weldingelectrodes have different weld face geometries, although here theworkpiece stack-up includes an additional steel workpiece (i.e., twosteel workpieces and one aluminum workpiece) according to one embodimentof the disclosure;

FIG. 20 is a general cross-sectional view of a workpiece stack-up, whichincludes a steel workpiece and an adjacent aluminum workpiece assembledin overlapping fashion, situated between a first welding electrode and asecond welding electrode in which the first and second weldingelectrodes have different weld face geometries, although here theworkpiece stack-up includes an additional aluminum workpiece (i.e., twoaluminum workpieces and one steel workpiece) according to one embodimentof the disclosure;

FIG. 21 is a general cross-sectional view of the workpiece stack-up andwelding electrodes shown in FIG. 18 during passage of electrical currentbetween the welding electrodes and through the stack-up, and wherein thepassage of electrical current has caused melting of the aluminumworkpiece that lies adjacent to the steel workpiece and the creation ofa molten aluminum weld pool within the aluminum workpiece;

FIG. 22 is a general cross-sectional view of the workpiece stack-up andwelding electrodes shown in FIG. 18 after passage of the electricalcurrent between the welding electrodes and through the stack-up hasceased, and wherein the molten aluminum weld pool has solidified into aweld joint that weld bonds the adjacent steel and aluminum workpiecestogether;

FIG. 23 depicts dressing of at least the weld faces of the first andsecond welding electrodes shown in FIGS. 9-10, wherein the first weldingelectrode (FIG. 9) is received in the first cutting socket of thecutting tool and the second welding electrode (FIG. 10) is received inthe second cutting socket;

FIG. 24 depicts dressing of at least the weld faces of the first andsecond welding electrodes shown in FIGS. 11-12, wherein the firstwelding electrode (FIG. 11) is received in the first cutting socket ofthe cutting tool and the second welding electrode (FIG. 12) is receivedin the second cutting socket; and

FIG. 25 depicts dressing of at least the weld faces of the first andsecond welding electrodes shown in FIGS. 13-14, wherein the firstwelding electrode (FIG. 13) is received in the first cutting socket ofthe cutting tool and the second welding electrode (FIG. 14) is receivedin the second cutting socket; and

FIG. 26 depicts dressing of at least the weld faces of the first andsecond welding electrodes shown in FIGS. 16-17, wherein the firstwelding electrode (FIG. 16) is received in the first cutting socket ofthe cutting tool and the second welding electrode (FIG. 17) is receivedin the second cutting socket.

DETAILED DESCRIPTION

A cutting tool is disclosed that can simultaneously cut and restoreasymmetric weld face geometries of two welding electrodes that aresubject to different degradation mechanisms. The cutting tool may beused as part of a method for resistance spot welding a workpiecestack-up that includes adjacent and overlapping steel and aluminumworkpieces. In particular, a first welding electrode with a first weldface and a second welding electrode with a second weld face may beemployed to pass an electrical current through the workpiece stack-up ata weld site. The geometry of the first weld face and the geometry of thesecond weld face are asymmetric because of the need to compensate forthe different physical properties of the steel and aluminum workpieces.Over time, the first and second weld faces become degraded to such anextent that spot welding operations are adversely affected. To addressthis issue, the cutting tool can be used to periodically redress boththe first and second weld faces of the first and second weldingelectrodes, respectively. Redressing the weld faces involves receivingthe first weld face in a first cutting socket and receiving the secondweld face in a second cutting socket, and then rotating the cutting toolabout the axes of the first and second weld faces to cut the weld facesand restore their geometries.

A cutting tool and a method of using the cutting tool in the context ofresistance spot welding a workpiece stack-up that includes adjacent andoverlapping steel and aluminum workpieces is described with reference toFIGS. 1-26. The cutting tool is constructed to simultaneously dress theweld faces of both welding electrodes even though the geometries of theweld faces are designed asymmetrically based on the significantdifferences in physical properties between the steel and aluminumworkpieces (e.g., melting point, thermal conductivity, electricalconductivity, strength at elevated temperatures, etc.). In this way, theweld faces of both welding electrodes can be periodically dressed withthe same cutting tool in a single operation to restore their originalunique geometries, as opposed to being separately dressed by their owndedicated cutting tools. Dressing the weld faces with the same cuttingtool is more efficient, and can be performed whenever desired tocounteract the weld face degradation mechanisms that, if allowed toprogress without intervention, would quickly compromise the weldingelectrodes and weld quality, and would eventually render them unfit forcontinued use in spot welding operations. The cutting tool may be usedto dress the weld faces as much as possible until the weld faces can nolonger support dressing due to the cumulative material loss attributedto the dressing operations.

A preferred embodiment of the cutting tool is shown in FIGS. 1-8 and isidentified by reference numeral 10. The cutting tool 10 comprises a body12 and a cutting member 14. The body 12 defines a through hole 16 thatextends longitudinally along a central axis 18 between a first opening20 at a first end 22 of the body 12 and a second opening 24 at a secondend 26 of the body 12. Each of the openings 20, 24 lies perpendicular tothe central axis 18 of the through hole 16 such that a plane 28 of thefirst opening 20 and a plane 30 of the second opening 22 are parallel toone another and are intersected by the central axis 18 at 90° angles, asshown in FIG. 4. The cutting member 14 is fixedly retained by the body12 within the through hole 16. The cutting member 14 establishes a firstcutting socket 32 and a second cutting socket 34. The first cuttingsocket 32 is accessible through the first opening 20 of the body 12 andthe second cutting socket 34 is accessible through the second opening 24of the body 12.

The body 12 and the cutting member 14 are constructed of a hard materialthat is capable of withstanding welding electrode dressing operations.For example, each of the body 12 and the cutting member 14 may be formedof a tool steel such as S7 or M2 tool steel. Furthermore, the cuttingmember 14 can be fixedly retained by the body 12 in a variety of waysthat renders those two portions of the tool 10 unable to move relativeto each other when the tool 10 is operational. In one embodiment, thebody 12 and the cutting member 14 may be discrete individual pieces thatare assembled and secured together to fabricate the cutting tool 10.This can be achieved in a number of ways including mechanical locking,fusion welding, brazing, soldering, adhesive bonding, or a combinationof any of these techniques. In another embodiment (schematicallydepicted in FIG. 27, for example), the body 12 and the cutting member 14are integrally formed, e.g., machined from a single solid piece of toolsteel, so as to constitute a single integral piece in the sense that thebody 12 and the cutting member 14 did not previously exist as discreteitems.

The body 12 includes an annular wall 36 that extends between the axiallyspaced apart first and second ends 22, 26 of the body 12. The annularwall 36 has an interior surface 38 and an exterior surface 40. Theinterior surface 38 of the annular wall 36 defines the through hole 16that passes through the body 12 including the first and second openings20, 24. The interior surface 38 has a base surface 42 and one or moredepressed surfaces 44 that are impressed into the annular wall 36 todelineate one or more retention channels 46. The one or more retentionchannels 46 serve to retain the cutting member 14 within the throughhole 16 in the event that the body 12 and the cutting member 14 are notintegrally formed. And, as shown here in FIG. 3, the retention channels46 may include a plurality of axial retention channels 46 a that extendaxially from the first end 22 of the body 12 to the second end 26 andare circumferentially spaced around the interior surface 38, and mayfurther include a circumferential retention channel 46 b that extendscircumferentially around the interior surface 38 and intersects each ofthe axial retention channels 46 a.

The exterior surface 40 of the annular wall 36 includes an integralretaining nut 48 and an integral radial flange 50. The integralretaining nut 48 protrudes from a central part of the annular wall 36between the first and second ends 22, 26 of the body 12 and has aplurality of planar surfaces 52 that intersect at circumferentiallyspaced axial edges 54 (FIG. 2). In a preferred embodiment, the integralretaining nut 48 includes six planar surfaces 52 of equal size arrangedhexagonally around the exterior surface 40 of the annular wall 36. Theintegral radial flange 50 adjoins and bears on an axial end of theintegral retaining nut 48 proximate either the first or second end 22,26 of the body 12. Here, in FIGS. 1-8, the integral radial flange 50 islocated proximate the first end 22, although it could just as easily belocated proximate the second end 26, if desired. The integral radialflange 50 extends radially outwardly beyond the planar surfaces 52 ofthe integral retaining nut 48 to provide a semicircular seating surface56 that projects transversely from each of the planar surfaces 52 asshown best in FIGS. 2 and 6. The combination of the integral retainingnut 48 and the integral radial flange 50 enables the cutting tool 10 tobe received and clutched within a rotatable cutting tool holder such as,for example, a chuck.

The cutting member 14 includes one or more cutting flutes 58 thatestablish the first and second cutting sockets 32, 34. The one or morecutting flutes 58 are constructed to dress weld faces that are receivedin the first and second cutting sockets 32, 34 and to restore asymmetricgeometries to those weld faces through a shearing action that resultswhen the cutting tool 10 is rotated about the central axis 18 of thethrough hole 16. Each of the cutting flutes 58 includes a blade 60 thatis supported at the interior surface 38 of the annular wall 36 by anelongate foot 62 that spans the entire axial dimension of the annularwall 36. Anywhere from one to four cutting flutes 58 may be present aspart of the cutting member 14. In a preferred embodiment, as shown herein FIGS. 1-6, the one or more cutting flutes 58 include a first cuttingflute 58 a, a second cutting flute 58 b, a third cutting flute 58 c, anda fourth cutting flute 58 d. The blades 60 and elongate feet 62 of thefour cutting flutes 58 a, 58 b, 58 c, 58 d are consequently identifiedin FIGS. 1-6 by reference numerals 60 a, 60 b, 60 c, 60 d and 62 a, 62b, 62 c, 62 d, respectively.

In the embodiment shown, each of the elongate feet 62 a, 62 b, 62 c, 62d is axially inserted into one of the axial retention channels 46 a ofthe interior surface 38 of the annular wall 36 and is held tightly inplace by friction due to the close complimentary shape of the retentionchannels 46 a and the elongate feet 62, as illustrated best in FIG. 3.Moreover, to further secure the cutting flutes 58 a, 58 b, 58 c, 58 d inplace, and to especially prevent unwanted axial movement of the cuttingflutes 58 a, 58 b, 58 c, 58 d within the through hole 16, a radialspring washer 64 that is radially outwardly biased into thecircumferential retention channel 46 b may be received in and extendthrough a transverse groove 66 defined in a back end of each of theelongate feet 62 a, 62 b, 62 c, 62 d. Other mechanisms for fixedlyretaining the cutting flutes 58 a, 58 b, 58 c, 58 d to the interiorsurface 38 of the annular wall 36 within the through hole 16 may beemployed in addition to or in lieu of the axially insertable elongatefeet 62 a, 62 b, 62 c, 62 d and the radial spring washer 64. To be sure,in another embodiment, and as previously indicated, the elongate feet 62a, 62 b, 62 c, 62 d of the cutting flutes 58 a, 58 b, 58 c, 58 d may beintegrally formed with the interior surface 38 of the annular wall 36such that the body 12 and the cutting member 14 constitute a singleintegral piece.

The blades 60 a, 60 b, 60 c, 60 d of the cutting flutes 58 a, 58 b, 58c, 58 d protrude inwardly from the interior surface 38 of the annularwall 36 and interconnect centrally within the through hole 16. Theblades 60 a, 60 b, 60 c, 60 d are circumferentially spaced from eachother at regular intervals about the central axis 18 such that eachblade 60 is oriented transverse to each of its two circumferentiallyadjacent blades 60. Each of the blades 60 a, 60 b, 60 c, 60 d includesaxially spaced apart and opposed first and second shearing surfaces 68,70. Specifically, in this embodiment, the blade 60 a of the firstcutting flute 58 a includes a first shearing surface 68 a proximate thefirst end 22 of the body 12 and a second shearing surface 70 a proximatethe second end 26 of the body 12. The blades 60 b, 60 c, 60 d of theother cutting flutes 58 b, 58 c, 58 d include similarly disposed firstand second shearing surfaces 68 b, 70 b, 68 c, 70 c, 68 d, 70 d relativeto the first and second ends 22, 26 of the body 12. Accordingly, in thisembodiment, the first and second cutting sockets 32, 34 established bythe cutting flutes 58 are defined collectively by the first shearingsurfaces 68 a, 68 b, 68 c, 68 d and the second shearing surfaces 70 a,70 b, 70 c, 70 d, respectively.

The first shearing surfaces 68 a, 68 b, 68 c, 68 d are profiled to cutand restore an electrode weld face of a first geometry and the secondshearing surfaces 70 a, 70 b, 70 c, 70 d are profiled to cut and restorean electrode weld face of a second geometry that is different than thefirst geometry. The different profiles of the first shearing surfaces 68a, 68 b, 68 c, 68 d and the second shearing surfaces 70 a, 70 b, 70 c,70 d permit the cutting tool 10 to restore the first weld face geometryto a welding electrode received in the first cutting socket 32 and,simultaneously, to restore the second weld face geometry to anotherwelding electrode received in the second cutting socket 34 while thetool 10 is being rotated about the central axis 18 of the through hole16. In this way, the cutting tool 10 is able to dress two weldingelectrodes with asymmetric weld face geometries, which is a usefuldressing practice when resistance spot welding is conducted withdisparate welding electrodes such as, for example, when the workpiecestack-up being welded includes an aluminum workpiece and an adjacentsteel workpiece.

The first and second weld face geometries that are cut by the firstshearing surface(s) 68 and the second shearing surface(s) 70,respectively, are designed to resistance spot weld a workpiece stack-upthat includes adjacent and overlapping steel and aluminum workpieces.The design of the weld face geometries is based in large part on thematerially different physical properties of the steel workpiece and thealuminum workpiece being spot welded together. In particular, the firstweld face geometry, which is deployed on the steel-side weldingelectrode, is designed to concentrate current within the steel workpiece(relative to the aluminum workpiece) and to also cause some deformationof the steel workpiece during electrical current flow. This takesadvantage of the low conductivity—both thermally and electrically—of thesteel workpiece as well as its elevated melting point relative to thealuminum workpiece. In a somewhat different fashion, the second weldface geometry, which is deployed on the aluminum-side electrode, isdesigned to break down the refractory oxide layer(s) on the aluminumworkpiece and to contain the molten aluminum weld pool that grows withinthe aluminum workpiece. Both the size and the shape of the second weldface geometry have an effect on containing the molten aluminum weld poolas it grows.

Referring now to FIGS. 1, 5, and 7, at least one of the first shearingsurfaces 68 a, 68 b, 68 c, 68 d includes a lower or proximal end portion72 and an upper or distal end portion 74 relative to an imaginary planeP oriented perpendicular to the central axis 18 and bisecting thecutting member 14. The lower or proximal end portion 72 is proximal tothe imaginary plane P and the upper or distal end portion is distal tothe imaginary plane P. The lower end portion 72 extends at least to thecentral axis 18 of the through hole 16 and has a leading edge 76 and atrailing edge 78. The leading edge 76 is upwardly profiled from a distaltip 80 and is contoured to cut at least the first weld face geometry andany surrounding transition nose into a welding electrode. Followingrestoration, the weld face with the first geometry has a specifieddiameter and, additionally, a specified planar or domed shape that mayinclude additional protruding or intruding surface features. Thetrailing edge 78 of the lower end portion 72 is upwardly profiled likethe leading edge 76 but is offset below the leading edge 76 such thatthe shearing surface 68 within the lower end portion 72 is inclined fromthe leading edge 76 to the trailing edge 78 at a positive relief anglethat ranges from 3° to 8°. The positive relief angle is illustratedgenerally in FIG. 7.

The upper end portion 74 of the first shearing surface 68 is convex inshape and extends from the lower end portion 72 to the elongate foot 62of the cutting flute 58. The upper end portion 74 has a leading edge 82and a trailing edge 84. These two edges 82, 84 may be offset by apositive relief angle like in the lower end portion 72, but they do notnecessarily have to since the upper end portion 74 is not necessarilyinvolved in cutting the first weld face geometry. Rather, the upper endportion 74 functions to center and guide the welding electrode downtowards the lower end portion 72 during rotation of the cutting tool 10about the central axis 18 of the through hole 16. Indeed, when a weldingelectrode is received in the first cutting socket 32 and the cuttingtool 10 is being rotated to restore the first weld face geometry, theupper end portion 74 of the shearing surface 68 typically does not makecontact with, and therefore does not cut, the neighboring regions of thewelding electrode that are outside of the weld face and transition nose.

Here, in the embodiment of FIGS. 1, 5, and 7, two of the aligned firstshearing surfaces 68 a, 68 c include the lower end portion 72 justdescribed, while the other two aligned first shearing surfaces 68 b, 68d include a variation of the lower end portion 72 in which the onlysignificant difference is that the distal tip 80 does not extend all theway to the central axis 18 of the through hole 16. Each of the fourshearing surfaces 68 a, 68 b, 68 c, 68 d also includes the upper endportion 74 described above for guiding and centering the weldingelectrode. All four of the first shearing surfaces 68 a, 68 b, 68 c, 68d are thus profiled in this embodiment to participate in cutting a weldface to restore the first geometry while also helping to align and guidethe weld face of the welding electrode into the proper position withinthe first cutting socket 32. The four shearing surfaces 68 a, 68 b, 68c, 68 d are employed together in this embodiment to make it easier andless time consuming to restore the first geometry.

Referring now to FIGS. 2, 6, and 8, at least one of the second shearingsurfaces 70 includes a lower or proximal end portion 86 and an upper ordistal end portion 88 relative to the imaginary plane P, much like thefirst shearing surface(s) 68. The lower or proximal end portion 86 isproximal to plane P and the upper or distal end portion 88 is distal toplane P. The lower end portion 86 extends at least to the central axis18 of the through hole 16 and has a leading edge 90 and a trailing edge92. The leading edge 90 is upwardly profiled from a distal tip 94 and iscontoured to cut at least the second weld face geometry and anysurrounding transition nose into a welding electrode. Followingrestoration, the weld face with the second geometry has a specifieddiameter and, additionally, a specified domed shape that may includeadditional protruding or intruding surface features. The trailing edge92 of the lower end portion 86 is upwardly profiled like the leadingedge 90 but is offset below the leading edge 90 such that the shearingsurface 70 within the lower end portion 86 is inclined from the leadingedge 90 to the trailing edge 92 at a positive relief angle that rangesfrom 3° to 8°. The positive relief angle is illustrated in FIG. 8.

The upper end portion 88 of the second shearing surface 70 is convex inshape and extends from the lower end portion 86 to the elongate foot 62of the cutting flute 58. The upper end portion 88 has a leading edge 96and a trailing edge 98. These two edges 96, 98 may be offset by apositive relief angle like in the lower end portion 86, but they do notnecessarily have to since the upper end portion 88 is not necessarilyinvolved in cutting the second weld face geometry. Rather, like before,the upper end portion 88 functions to center and guide the weldingelectrode down towards the lower end portion 86 during rotation of thecutting tool 10 about the central axis 18 of the through hole 16.Indeed, when a welding electrode is received in the second cuttingsocket 34 and the cutting tool 10 is being rotated to restore the secondweld face geometry, the upper end portion 88 of the second shearingsurface 70 typically does not make contact with, and therefore does notcut, the neighboring regions of the welding electrode that are outsideof the weld face and the transition nose.

In the embodiment of FIGS. 2, 6, and 8, two of the aligned secondshearing surfaces 70 b, 70 d include the lower end portion 86 justdescribed, while the other two aligned second shearing surfaces 70 a, 70c include a variation of the lower end portion 86 in which the onlysignificant difference is that the distal tip 94 does not extend all theway to the central axis 18 of the through hole 16. Each of the secondshearing surfaces 70 a, 70 b, 70 c, 70 d also includes the upper endportion 88 as described above for guiding and centering the electrode.All four of the second shearing surfaces 70 a, 70 b, 70 c, 70 d are thusprofiled in this embodiment to participate in cutting a weld face torestore the second geometry while also helping to align and guide theweld face of the welding electrode into the proper position within thesecond cutting socket 34. The four shearing surfaces 70 a, 70 b, 70 c,70 d are employed together in this embodiment to make it easier and lesstime consuming to restore the first geometry. Moreover, as shown, thesecond shearing surfaces 70 b, 70 d that have distal tips 94 extendingto the central axis 18 of the through hole 16 are not present on thesame blades 60 as the first shearing surfaces 68 a, 68 c that similarlyhave distal tips 80 extending to the central axis 18 of the through hole16. The two sets of first and second shearing surfaces 68 a, 68 c, 70 b,70 d are, instead, oriented transverse to one another on the cuttingmember 14.

It should be appreciated that other cutting flute designs that areconstructed to dress the asymmetric first and second weld facesgeometries are of course possible and may be used as an alternative tothe cutting flutes 58 a, 58 b, 58 c, 58 d—with their opposed first andsecond shearing surfaces 68 a, 68 b, 68 c, 68 d, 70 a, 70 b, 70 c, 70d—shown in the Figures and described above. The cutting member 14 may,for example, include only one cutting flute 58 with a first shearingsurface 68 and a second shearing surface 70. The axially spaced apartfirst and second shearing surfaces 68, 70 may include the lower endportions 72, 86 described above. In another example, the cutting member14 may include two opposed cutting flutes 58, each of which has a firstshearing surface 68 and a second shearing surface 70. The first shearingsurfaces 68 and the second shearing surfaces 70 of the opposed cuttingflutes 58 may be constructed in the same way as surfaces 68 a, 68 c andsurfaces 70 b, 70 d, respectively, as described above.

The first and second weld face geometries may that may be cut andrestored by the first and second cutting sockets 32, 34, respectively,can assume a variety of configurations. Some of the specificcombinations of first and second weld face geometries are depicted inFIGS. 9-14. In these examples, the first and second weld face geometriesare designed for resistance spot welding workpiece stack-ups thatinclude adjacent overlapping steel and aluminum workpieces. Thedisparate weld face geometries are employed to try and address theunique challenges posed by the dissimilar steel and aluminum workpiecesduring resistance spot welding and to ultimately make it easier toconsistently attain weld joints with good strength properties. While theparticular weld face geometries illustrated in FIGS. 9-14 and describedin the following text are useful in combination with one another, itshould be understood that other weld face geometries may be adapted toachieve similar objectives despite not being expressly shown anddescribed here.

One specific combination of weld face geometries is depicted in FIGS.9-10. There, a welding electrode 200 (also referred to as the “firstwelding electrode 200”) that includes the first weld face geometry andis dressable by the first shearing surface(s) 68 of the one or morecutting flutes 58 is shown in FIG. 9, and a welding electrode 220 (alsoreferred to as the “second welding electrode 220”) that includes thesecond weld face geometry and is dressable by the second shearingsurface(s) 70 of the one or more cutting flutes 58 is shown in FIG. 10.The first and second welding electrodes 200, 220 may be constructed fromany electrically and thermally conductive material suitable for spotwelding applications that may experience degradation during welding. Forexample, the welding electrodes 200, 220 may be constructed from acopper alloy having an electrical conductivity of at least 80% IACS, ormore preferably at least 90% IACS, and a thermal conductivity of atleast 300 W/mK, or more preferably at least 350 W/mK. One specificexample of a copper alloy that may be used is a copper-zirconium alloy(CuZr) that contains about 0.10 wt % to about 0.20 wt % zirconium andthe balance copper. Copper alloys that meet this constituent compositionand are designated C15000 are preferred. Other suitable materials fromwhich the welding electrodes 200, 220 may be formed include C18200copper-chromium (CuCr) alloy, C18150 copper-chromium-zirconium (CuCrZr)alloy, or a refractory-based metal composite such as a tungsten-coppercomposite.

The first welding electrode 200 includes an electrode body 202 and aweld face 204. The electrode body 202 is preferably cylindrical in shapeand includes a front end 206 having a circumference 2060. A diameter2062 of the body 202 at its front end circumference 2060 preferably lieswithin the range of 12 mm to 22 mm or, more narrowly, within the rangeof 16 mm to 20 mm. The weld face 204 is disposed on the front end 206 ofthe body 202 and has a circumference 2040 that is coincident with thecircumference 2060 of the front end 206 of the body 202 (a “full faceelectrode”) or is upwardly displaced from the circumference 2060 of thefront end 206, to a distance between 2 mm and 10 mm, by a transitionnose 208 of frustoconical or truncated spherical shape. If thetransition nose 208 is frustoconical, the angle of truncation ispreferably between 15° and 40° from a horizontal plane of the weld facecircumference 2040. If the transition nose 208 is spherical, the radiusof curvature of the transition nose 208 preferably ranges between 6 mmand 20 mm or, more narrowly, between 8 mm and 12 mm.

The weld face 204 preferably has a diameter 2042 measured at itscircumference 2040 that lies within the range of 3 mm to 16 mm or, morenarrowly, within the range of 4 mm to 8 mm. In terms of its shape, theweld face 204 includes a base weld face surface 210 that may be planaror domed. If domed, the base weld face surface 210 ascends upwardly andinwardly from the circumference 2040 of the weld face 204 to attain anupwardly curved convex shape. For example, in one particular embodiment,the base weld face surface 210 may be spherically domed in that it has aspherical profile with a radius of curvature that preferably lies withinthe range of 8 mm to 400 mm or, more narrowly, within the range of 25 mmto 100 mm. The geometry of the weld face 204—whether planar or domed inshape with its prescribed diameter 2042—may be cut and restored byreceiving the degraded weld face 204 in the first cutting socket 32 ofthe cutting tool 10 and then rotating the tool 10 about an axis 212 ofthe weld face 204. In doing so, the first shearing surface(s) 68 of theone or more cutting flutes 58 shear off weld face material to exposefresh weld face material and to restore the first weld face geometry.

The second electrode 220 includes an electrode body 222 and a weld face224. The electrode body 222 is preferably cylindrical in shape andincludes a front end 226 having a circumference 2260. A diameter 2262 ofthe body 222 taken at its front end circumference 2260 preferably lieswithin the range of 12 mm to 22 mm or, more narrowly, within the rangeof 16 mm to 20 mm. The weld face 224 is disposed on the front end 226 ofthe body 222 and has a circumference 2240 that is coincident with thecircumference 2260 of the front end 226 of the body 222 (a “full faceelectrode”) or is upwardly displaced from the circumference 2260 of thefront end 226, to a distance between 2 mm and 10 mm, by a transitionnose 228 of frustoconical or truncated spherical shape. If thetransition nose 228 is frustoconical, the angle of truncation ispreferably between 30° and 60° from a horizontal plane of the weld facecircumference 2040. If the transition nose 228 is spherical, the radiusof curvature of the transition nose 228 preferably ranges between 6 mmand 12 mm.

The weld face 224 preferably has a diameter 2242 measured at itscircumference 2240 that lies within the range of 8 mm to 20 mm or, morenarrowly, within the range of 10 mm to 15 mm. In terms of its shape, theweld face 224 includes a base weld face surface 230 and a centralplateau 232. The base weld face surface 230 is domed and thus ascendsupwardly and inwardly from the circumference 2240 of the weld face 224to attain an upwardly curved convex shape. For example, in oneparticular embodiment, the base weld face surface 230 may be sphericallydomed in that it has a spherical profile with a radius of curvature thatpreferably lies within the range of 15 mm to 300 mm or, more narrowly,within the range of 20 mm to 50 mm. The central plateau 232 is centeredon the base weld face surface 230 about an axis 234 of the weld face 224and is surrounded by an annular portion of the base weld face surface230. The central plateau 232 is a surface feature that enables thesecond welding electrode 220 to be used in conjunction with many typesof workpiece stack-ups during resistance spot welding operations asdescribed in U.S. Pat. No. 8,525,066. In addition to the central plateau232, the weld face 224 may also include upstanding circular ridges orintruding circular grooves (relative to the base weld face surface 230)surrounding the central plateau 232, if desired.

The central plateau 232 includes a plateau surface 236 and a sidesurface 238. The plateau surface 236 is positively displaced above thesurrounding base weld face surface 230 by 0.1 mm to 0.5 mm and isflatter than the base weld face surface 230. For instance, the plateausurface 236 may be planar or it may have a spherical radius of curvaturethat is greater than the spherical radius of curvature of the base weldface surface 230. If spherically shaped, the radius of curvature of theplateau surface 236 is preferably 40 mm or greater. Additionally, theplateau surface 236 may be circular in plan view (i.e., top down view)and the side surface 238 that positively displaces the plateau surface236 above the base weld face surface 230 may be cylindrical in shape.The plateau surface 236, if circular in plan view, may have a diameterthat ranges from 3 mm to 7 mm.

The second geometry of the weld face 224—in particular the domed baseweld face surface 230 with the upstanding central plateau 232 and theprescribed diameter 2242 of the weld face 224—may be cut and restored byreceiving the degraded weld face 224 in the second cutting socket 34 ofthe cutting tool 10 and then rotating the tool 10 about the axis 234 ofthe weld face 224. In doing so, the central plateau 232 on the weld face224 is registered in a corresponding intrusion that extends at leastpart of the way from the leading edge 90 to the trailing edge 92 of thelower end portion 86 of the second shearing surface(s) 70 of the one ormore cutting flutes 58, and the rotation of the cutting tool 10 shearsoff weld face material to expose fresh weld face material and to restorethe second weld face geometry. The first and second weld face geometriesof the first and second welding electrodes 200, 220 may be restoredsimultaneously by rotating the cutting tool 10 while both the first weldface 204 and the second weld face 224 are received in the first andsecond cutting sockets 32, 34, respectively.

Another specific combination of weld face geometries is depicted inFIGS. 11-12. There, a welding electrode 300 (also referred to as the“first welding electrode 300”) that includes the first weld facegeometry and is dressable by the first shearing surface(s) 68 of the oneor more cutting flutes 58 is shown in FIG. 11, and a welding electrode320 (also referred to as the “second welding electrode 320”) thatincludes the second weld face geometry and is dressable by the secondshearing surface(s) 70 of the one or more cutting flutes 58 is shown inFIG. 12. The first and second welding electrodes 300, 320 may beconstructed from any electrically and thermally conductive materialsuitable for spot welding applications that may experience degradationduring welding. For example, as before, the welding electrodes 300, 320may be constructed from a copper alloy having an electrical conductivityof at least 80% IACS, or more preferably at least 90% IACS, and athermal conductivity of at least 300 W/mK, or more preferably at least350 W/mK, as well as other electrically and thermally conductivematerials.

The first welding electrode 300 is the same as the first weldingelectrode 200 illustrated in FIG. 9. In particular, the first weldingelectrode 300 includes a body 302 and a weld face 304 that arestructurally the same as the body 202 and the weld face 204 of thepreviously described first welding electrode 200. Correspondingreference numerals are therefore used in FIG. 11 to denote structuralaspects of the first welding electrode 300 that are the same as those ofthe previously described first welding electrode 200 and to furtherincorporate the disclosure above regarding those similar structuralattributes. Given the structural similarity between the two electrodes200, 300, a redundant description of the first welding electrode 300 ofFIG. 11 is not needed here. The difference in the weld face geometrycombination of FIGS. 11-12 compared to FIGS. 9-10 is based solely on thesecond welding electrode 320 illustrated in FIG. 12.

The second welding electrode 320 is similar in many respects to thesecond welding electrode 220 illustrated in FIG. 10. Here, as shown, thesecond welding electrode 320 includes a body 322 and a weld face 324that are structurally the same as the body 222 and the weld face 224 ofthe previously described second welding electrode 220—and are thusidentified with corresponding reference numerals—with the exception thatthe weld face 324 additionally includes a plurality of terraces 340surrounding a central plateau 332. The plurality of terraces 340 mayinclude anywhere from two to ten terraces 340, each of which includes atop terrace surface 342 and a side surface 344 joined by a roundedcircumferential shoulder surface 346. The top terrace surface 342 ofeach terrace 340 is displaced axially below the top terrace surface 342of its radially inward neighboring terrace 340 or, in the case of theterrace 340 that immediately surrounds the central plateau 332, aplateau surface 336. The top terrace surface 342 of each terrace 340 maybe planar or spherically shaped with a radius of curvature that rangesfrom 100 mm to 400 mm, and the shoulder surfaces 346 of the plurality ofterraces 340 are preferably separated by a radial distance that rangesfrom 200 μm to 1500 μm.

The plurality of terraces 340 are contiguous with each other startingfrom a side surface 338 of the central plateau 332; that is, the topterrace surface 342 of each terrace 340 intersects and extends radiallyoutwardly from the side surface 344 of its radially inward neighboringterrace 340 (or the side surface 338 of the central plateau 332 in thecase of the innermost terrace 340). Indeed, in the embodiment shownhere, the weld face 324 of the second welding electrode 320 includesthree terraces 340. A first terrace 340 a is contiguous with the centralplateau 332 and includes a top terrace surface 342 a that extends fromthe side surface 338 of the central plateau 332 to its own side surface344 a. A second terrace 340 b is continuous with the first terrace 340 aand includes a top terrace surface 342 b that extends from the sidesurface 344 a of the first terrace 340 a to its own side surface 344 b.And, similarly, a third terrace 340 c is continuous with the secondterrace 340 b and includes a top terrace surface 342 c that extends fromthe side surface 344 b of the second terrace 340 b to its own sidesurface 344 c. Any additional terraces 340 that may be present radiallyoutside of the third terrace 344 c are contiguous in this same way withthe rest of the terraces 340.

The first and second geometries of the weld faces 304, 324 may be cutand restored by receiving the degraded weld face 304, 324 in the firstand second cutting sockets 32, 34 of the cutting tool 10, respectively,and then rotating the tool 10 about the axes 312, 334 of the weld faces304, 324 as previously described with respect to FIGS. 9-10. The maindifference here is that the second weld face 324 now includes aplurality of terraces 340 in addition to the central plateau 332. Inthat regard, the second shearing surface(s) 70 of the one or morecutting flutes 58 now include multiple intrusions that extend at leastpart of the way from the leading edge 90 to the trailing edge 92 of thelower end portion 86. The central plateau 332 and the plurality ofterraces 340 are registered within those corresponding intrusions sothat, during rotation of the cutting tool 10, the second shearingsurface(s) 70 shears off weld face material to expose fresh weld facematerial and to restore the second weld face geometry.

Another specific combination of weld face geometries is depicted inFIGS. 13-14. There, a welding electrode 420 (also referred to as the“first welding electrode 420”) that includes the first weld facegeometry and is dressable by the first shearing surface(s) 68 of the oneor more cutting flutes 58 is shown in FIG. 13, and a welding electrode520 (also referred to as the “second welding electrode 520”) thatincludes the second weld face geometry and is dressable by the secondshearing surface(s) 70 of the one or more cutting flutes 58 is shown inFIG. 14. The first and second welding electrodes 420, 520 may beconstructed from any electrically and thermally conductive materialsuitable for spot welding applications that may experience degradationduring welding. For example, as before, the welding electrodes 420, 520may be constructed from a copper alloy having an electrical conductivityof at least 80% IACS, or more preferably at least 90% IACS, and athermal conductivity of at least 300 W/mK, or more preferably at least350 W/mK, as well as other electrically and thermally conductivematerials.

The first welding electrode 420 is the same as the second weldingelectrode 220 illustrated in FIG. 10. In particular, the first weldingelectrode 420 includes a body 422 and a weld face 424 that arestructurally the same as the body 222 and the weld face 224 of thepreviously described second welding electrode 220. Correspondingreference numerals are therefore used in FIG. 13 to denote structuralaspects of the first welding electrode 420 that are the same as those ofthe previously described second welding electrode 220 and to furtherincorporate the disclosure above regarding those similar structuralattributes. Given the structural similarity between the two electrodes420, 220, a redundant description of the first welding electrode 420 ofFIG. 13 is not needed here. Like the first welding electrode 420, thesecond welding electrode 520 also includes at least one weld facesurface feature.

The second electrode 520 is similar in many respects to the secondwelding electrode 220 illustrated in FIG. 10. Here, as shown, the secondwelding electrode 520 includes a body 522 and a weld face 524 that arestructurally the same as the previously described second weldingelectrode 220—and are thus identified with corresponding referencenumerals—with the exception that the weld face 524 does not include acentral plateau, but, rather, includes a series of upstanding circularridges 550. These upstanding circular ridges 550 project outwardly froma base weld face surface 530 and enable the second welding electrode 520to establish good mechanical and electrical contact with an aluminumworkpiece surface by stressing and fracturing the mechanically tough andelectrically insulating refractory oxide layer(s) that typically coatthe surface of an aluminum workpiece.

The series of upstanding circular ridges 550 are preferably centeredabout and surround an axis 534 of the weld face 524. The base weld facesurface 530 from which the ridges 550 project may account for 50% ormore, and preferably between 50% and 80%, of the surface area of theweld face 524. The remaining surface area is attributed to the series ofupstanding circular ridges 550, which preferably includes anywhere fromtwo to ten ridges 550, or more narrowly from three to five ridges 550.The several upstanding circular ridges 550 are radially spaced apartfrom each other on the base weld face surface 530 such that theupstanding ridges 550 become larger in diameter when moving from theinnermost upstanding ridge 550 a (FIG. 15) that immediately surroundsthe axis 534 of the weld face 524 to the outermost upstanding ridge 550b (FIG. 15) that is most proximate to the circumference 5240 of the weldface 524 and, thus, furthest from the axis 534 of the weld face 524.

The size and shape of the upstanding circular ridges 550 are subject tosome variability without sacrificing their dressability. In oneembodiment, as shown best in FIG. 14, each of the upstanding circularridges 550 has a closed circumference, meaning the circumference of theridge 550 is continuously curved and thus not interrupted by significantseparations, and is additionally defined by a cross-sectional profilethat lacks sharp corners while having a curved (as shown) or flat topsurface. Moreover, as shown in FIG. 15, each of the circular ridges 550also has a ridge height 550 h—taken at the midpoint of the ridge550—that extends upwards from the base weld face surface 530 when viewedin cross-section. The ridge height 550 h of each ridge 550 preferablyranges from 20 μm to 500 μm or, more narrowly, from 50 μm to 300 μm. Andthe spacing of the ridges 550 as measured between the midpoints of twoadjacent ridges 550 preferably ranges from 50 μm to 1800 μm or, morenarrowly, from 80 μm to 1500 μm. Each of the circular ridges 550 ispreferably semicircular, truncated semicircular, or triangular incross-section.

The first and second geometries of the weld faces 424, 524 may be cutand restored by receiving the degraded weld face 424, 524 in the firstand second cutting sockets 32, 34 of the cutting tool 10, respectively,and then rotating the tool 10 about the axes 434, 534 of the weld faces424, 524. The first weld face 424, more specifically, is cut by thefirst shearing surface(s) 68 of the one or more cutting flutes 58. Indoing so, and in much the same way as in FIG. 10, the central plateau432 on the weld face 424 is registered in a corresponding intrusion thatextends at least part of the way from the leading edge 76 to thetrailing edge 78 of the lower end portion 72 of the first shearingsurface(s) 68 of the one or more cutting flutes 58, and the rotation ofthe cutting tool 10 shears off weld face material to expose fresh weldface material and to restore the first weld face geometry.

The second weld face 524 is cut by the second cutting surface(s) 70 ofthe one or more cutting flutes 58. In order to do so, the secondshearing surface 70 of the one or more of the cutting flutes 58 definesa plurality of intruding grooves that extend from the leading edge 90 atleast part of the way to the trailing edge 92 within the lower endportion 86. The intruding grooves, which may be straight or curvedacross the second shearing surface(s) 70, preferably include between twoand ten grooves that extend all the way across the shearing surface(s)70 from the leading edge 90 to the trailing edge 92. Each of theintruding grooves has a height (measured as the maximum intrudingdistance from the shearing surface 70 at the leading edge 90) thatranges from 20 μm to 500 μm or, more narrowly, from 50 μm to 300 μm.Additionally, the intruding grooves are spaced apart along the shearingsurface 70 (measured as the distance between the midpoints of adjacentgrooves along the shearing surface 70 at the leading edge 90) thatranges from 50 μm to 1800 μm or, more narrowly, from 80 μm to 1500 μm.In a preferred embodiment, the bottom of each of the intruding grooveshas a constant radius of curvature to create a blunt or rounded shape incross-section, although other alternative cross-sectional shapes arecertainly possible including truncated semicircular and triangular.

The intruding grooves may extend from the leading edge 90 across thesecond shearing surface(s) 70 at a positive relief angle that is thesame or different from the relief angle of the shearing surface 70. Inparticular, the positive relief angle of the intruding grooves from theleading edge 90 towards the trailing edge 92 may range from 1.5° to 20°or, more narrowly, from 5° to 15°. If the intruding grooves extendstraight across the second shearing surface 70, the relief angle of thegrooves is preferably greater than 8° to allow enough clearance betweenthe interior groove walls and the upstanding ridges being cut andrestored during rotation of the cutting tool 10. If, however, theintruding grooves are curved across the second shearing surface 70 tomatch the curvature of the ridges being cut and restored, the positiverelief angle can be the same or even less (e.g., down to 1.5°) than therelief angle of the second shearing surface 70 since the curvature ofthe grooves naturally limits interference between the interior groovewalls and the ridges being cut and restored. A discussion of anembodiment of intruding grooves that may be incorporated into the secondshearing surface(s) 70 is included in U.S. application Ser. No.15/418,768, the entire contents of which are incorporated herein byreference.

Still another specific combination of weld face geometries is depictedin FIGS. 16-17. There, a welding electrode 620 (also referred to as the“first welding electrode 620”) that includes the first weld facegeometry and is dressable by the first shearing surface(s) 68 of the oneor more cutting flutes 58 is shown in FIG. 16, and a welding electrode720 (also referred to as the “second welding electrode 720”) thatincludes the second weld face geometry and is dressable by the secondshearing surface(s) 70 of the one or more cutting flutes 58 is shown inFIG. 17. The first and second welding electrodes 620, 720 may beconstructed from any electrically and thermally conductive materialsuitable for spot welding applications that may experience degradationduring welding. For example, as before, the welding electrodes 620, 720may be constructed from a copper alloy having an electrical conductivityof at least 80% IACS, or more preferably at least 90% IACS, and athermal conductivity of at least 300 W/mK, or more preferably at least350 W/mK, as well as other electrically and thermally conductivematerials.

The first welding electrode 620 is the same as the second weldingelectrode 220 illustrated in FIG. 10, and the second welding electrode720 is the same as the second welding electrode 320 illustrated in FIG.12. In particular, the first welding electrode 620 includes a body 622and a weld face 624 that are structurally the same as the body 222 andthe weld face 224 of the previously described second welding electrode220. Likewise, the second welding electrode 720 includes a body 722 anda weld face 724 that are structurally the same as the body 322 and theweld face 324 of the previously described second welding electrode 320.Corresponding reference numerals are therefore used in FIGS. 16-17 todenote structural aspects of the first and second welding electrodes620, 720 that are the same as those of the previously described secondwelding electrodes 220, 320 and to further incorporate the disclosureabove regarding those similar structural attributes. Given thestructural similarity between the two electrodes 220, 620, 320, 720, aredundant description of the first and second welding electrodes 620,720 of FIGS. 16-17 is not needed here.

The first and second geometries of the weld faces 624, 724 may be cutand restored by receiving the degraded weld face 624, 724 in the firstand second cutting sockets 32, 34 of the cutting tool 10, respectively,and then rotating the tool 10 about the axes 634, 734 of the weld faces624, 724. More specifically, the first weld face 624 is cut by the firstshearing surface(s) 68 of the one or more cutting flutes 58 and thesecond weld face 724 is cut by the second shearing surface(s) 70. Indoing so, and in much the same way as in FIG. 10, the central plateau632 of the first weld face 624 is registered in a correspondingintrusion that extends at least part of the way from the leading edge 76to the trailing edge 78 of the lower end portion 72 of the firstshearing surface(s) 68 of the one or more cutting flutes 58, and therotation of the cutting tool 10 shears off weld face material to exposefresh weld face material and to restore the first weld face geometry.Likewise, in much the same way as in FIG. 12, the central plateau 732and the plurality of terraces 740 of the second weld face 724 areregistered in corresponding intrusions that extend at least part of theway from leading edge 90 to the trailing edge 92 of the lower endportion 86 of the second shearing surface(s) 70 of the one or morecutting flutes 58, and the rotation of the cutting tool 10 shears offweld face material to expose fresh weld face material and to restore thesecond weld face geometry.

The cutting tool 10 may be used to dress a pair of welding electrodes,as needed, that are engaged in resistance spot welding a workpiecestack-up 800 that includes dissimilar workpieces, as shown in FIGS.18-26. The workpiece stack-up 800 has a first side 802 and a second side804 and includes at least a steel workpiece 806 and an aluminumworkpiece 808 that overlap with and lie adjacent to one another toestablish a faying interface 810 that extends through a weld site 812.The first side 802 of the workpiece stack-up 800 is provided by a steelworkpiece surface 814 and the second side 804 is provided by an aluminumworkpiece surface 816. The workpiece stack-up 800 may, thus, be a “2T”stack-up that includes only the adjacent pair of steel and aluminumworkpieces 806, 808, or it may be a “3T” stack-up that includes theadjacent steel and aluminum workpieces 806, 808 plus an additional steelworkpiece 818 (steel-steel-aluminum as shown in FIG. 19) or anadditional aluminum workpiece 820 (steel-aluminum-aluminum as shown inFIG. 20) so long as the two workpieces of the same base metalcomposition are disposed next to each other. In other embodiments, theworkpiece stack-up 800 may even be a “4T” stack-up such assteel-steel-steel-aluminum, steel-steel-aluminum-aluminum, orsteel-aluminum-aluminum-aluminum).

The steel workpiece 806 includes a steel substrate of any of a widevariety of strengths and grades that is either coated or uncoated (i.e.,bare). The coated or uncoated steel substrate may be hot-rolled orcold-rolled and may be composed of any of steel such as mild steel,interstitial-free steel, bake-hardenable steel, high-strength low-alloy(HSLA) steel, dual-phase (DP) steel, complex-phase (CP) steel,martensitic (MART) steel, transformation induced plasticity (TRIP)steel, twining induced plasticity (TWIP) steel, and boron steel such aswhen the steel workpiece 806 includes press-hardened steel (PHS). Ifcoated, the steel substrate preferably includes a surface layer of zinc(e.g., hot-dip galvanized or electrogalvanized), zinc-iron (galvanneal),a zinc-nickel alloy, nickel, aluminum, or an aluminum-silicon alloy. Theterm “steel workpiece” as used herein thus encompasses a wide variety ofsteel substrates, whether coated or uncoated, of different grades andstrengths, and further includes those that have undergone pre-weldingtreatments like annealing, quenching, and/or tempering such as in theproduction of press-hardened steel. Taking into account the thickness ofthe steel substrate and any surface coating that may be present, thesteel workpiece 806 has a thickness 8060 that ranges from 0.3 mm and 6.0mm, or more narrowly from 0.6 mm to 2.5 mm, at least at the weld site812.

The aluminum workpiece 808 includes an aluminum substrate that is eithercoated or uncoated (i.e., bare). The aluminum substrate may be composedof unalloyed aluminum or an aluminum alloy that includes at least 85 wt% aluminum. Some notable aluminum alloys that may constitute the coatedor uncoated aluminum substrate are an aluminum-magnesium alloy, analuminum-silicon alloy, an aluminum-magnesium-silicon alloy, or analuminum-zinc alloy. If coated, the aluminum substrate preferablyincludes a surface layer of its native refractory oxide layer(s), or,alternatively, it may include a surface layer of zinc, tin, or a metaloxide conversion coating comprised of oxides of titanium, zirconium,chromium, or silicon, as described in US2014/0360986. Taking intoaccount the thickness of the aluminum substrate and any surface coatingthat may be present, the aluminum workpiece 808 has a thickness 8080that ranges from 0.3 mm to about 6.0 mm, or more narrowly from 0.5 mm to3.0 mm, at least at the weld site 812.

The aluminum substrate of the aluminum workpiece 808 may be provided inwrought or cast form. For example, the aluminum substrate may becomposed of a 4xxx, 5xxx, 6xxx, or 7xxx series wrought aluminum alloysheet layer, extrusion, forging, or other worked article. Alternatively,the aluminum substrate may be composed of a 4xx.x, 5xx.x, or 7xx.xseries aluminum alloy casting. Some more specific kinds of aluminumalloys that may constitute the aluminum substrate include, but are notlimited to, AA5182 and AA5754 aluminum-magnesium alloy, AA6011 andAA6022 aluminum-magnesium-silicon alloy, AA7003 and AA7055 aluminum-zincalloy, and Al-10Si-Mg aluminum die casting alloy. The aluminum substratemay further be employed in a variety of tempers including annealed (O),strain hardened (H), and solution heat treated (T), if desired. The term“aluminum workpiece” as used herein thus encompasses unalloyed aluminumand a wide variety of aluminum alloy substrates, whether coated oruncoated, in different spot-weldable forms including wrought sheetlayers, extrusions, forgings, etc., as well as castings, and furtherincludes those that have undergone pre-welding treatments such asannealing, strain hardening, and solution heat treating.

The steel workpiece surface 814 and the aluminum workpiece surface 816that provide the first and second sides 802, 804 of the workpiecestack-up 800 may be presented by the adjacent and overlapping steel andaluminum workpieces 806, 808. For example, when the two workpieces 806,808 are stacked-up for spot welding in the context of the embodimentshown in FIG. 18, the steel workpiece 806 includes a faying surface 822and an exterior outer surface 824 and, likewise, the aluminum workpiece808 includes a faying surface 826 and an exterior outer surface 828. Thefaying surfaces 822, 826 of the two workpieces 806, 808 overlap andcontact one another to establish the faying interface 810 that extendsthrough the weld site 812. The exterior outer surfaces 824, 828 of thesteel and aluminum workpieces 806, 808, on the other hand, face awayfrom one another in opposite directions at the weld site 812 andconstitute the steel and aluminum workpiece surfaces 814, 816,respectively, of the workpiece stack-up 800.

The term “faying interface 810” is used broadly in the presentdisclosure and is intended to encompass instances of direct and indirectcontact between the faying surfaces 822, 826 of the adjacent steel andaluminum workpieces 806, 808. The faying surfaces 822, 826 are in directcontact with each other when they physically abut and are not separatedby a discrete intervening material layer. The faying surfaces 822, 826are in indirect contact with each other when they are separated by adiscrete intervening material layer—and thus do not experience the typeof interfacial physical abutment found in direct contact—yet are inclose enough proximity to each other that resistance spot welding canstill be practiced. Indirect contact between the faying surfaces 822,826 of the steel and aluminum workpieces 806, 808 typically results whenan optional intermediate material layer (not shown) is applied betweenthe faying surfaces 822, 826 before the workpieces 806, 808 aresuperimposed against each other during formation of the workpiecestack-up 800.

An intermediate material layer that may be present between the fayingsurfaces 822, 826 of the adjacent steel and aluminum workpieces 806, 808is an uncured yet heat-curable structural adhesive. Such an intermediatematerial typically has a thickness of 0.1 mm to 2.0 mm, which permitsspot welding through the intermediate layer without much difficulty. Astructural adhesive may be disposed between the faying surfaces 822, 826of the steel and aluminum workpieces 806, 808 so that, following spotwelding, the workpiece stack-up 800 can be heated in an ELPO-bake ovenor other apparatus to cure the adhesive and provide additional bondingbetween the workpieces 806, 808. A specific example of a suitableheat-curable structural adhesive is a heat-curable epoxy that mayinclude filler particles, such as silica particles, to modify theviscosity or other mechanical properties of the adhesive when cured. Avariety of heat-curable epoxies are commercially available including DOWBetamate 1486, Henkel 5089, and Uniseal 2343. Other types of materialsmay certainly constitute the intermediate material layer in lieu of aheat-curable structural adhesive.

Of course, as shown in FIGS. 19-20, the workpiece stack-up 800 is notlimited to the inclusion of only the steel workpiece 806 and theadjacent aluminum workpiece 808. The workpiece stack-up 800 may alsoinclude the additional steel workpiece 818 or the additional aluminumworkpiece 820—in addition to the adjacent steel and aluminum alloyworkpieces 806, 808—so long as the additional workpiece is disposedadjacent to the workpiece 806, 808 of the same base metal composition;that is, the additional steel workpiece 818 (if present) is disposedadjacent to the other steel workpiece 806 and the additional aluminumworkpiece 820 (if present) is disposed adjacent to the other aluminumworkpiece 808. As for the characteristics of the additional workpiece,the descriptions of the steel workpiece 806 and the aluminum workpiece808 provided above are applicable to the additional steel or theadditional aluminum workpiece that may be included in the workpiecestack-up 800. It should be noted, though, that while the same generaldescriptions apply, there is no requirement that the two steelworkpieces or the two aluminum workpieces of a 3T stack-up be identicalin terms of composition, thickness, or form (e.g., wrought or cast).

As shown in FIG. 19, for example, the workpiece stack-up 800 may includethe adjacent steel and aluminum workpieces 806, 808 described abovealong with the additional steel workpiece 818 that overlaps and isdisposed adjacent to the steel workpiece 806. When the additional steelworkpiece 818 is so positioned, the exterior outer surface 828 of thealuminum workpiece 808 constitutes the aluminum workpiece surface 816that provides the second side 804 of the workpiece stack-up 800, asbefore, while the steel workpiece 806 that lies adjacent to the aluminumworkpiece 808 now includes a pair of opposed faying surfaces 822, 830.The faying surface 822 of the steel workpiece 806 that confronts andcontacts (directly or indirectly) the adjacent faying surface 826 of thealuminum workpiece 808 establishes the faying interface 810 between thetwo workpieces 806, 808 as previously described. The other fayingsurface 830 of the steel workpiece 806 confronts and makes overlappingcontact (direct or indirect) with a faying surface 832 of the additionalsteel workpiece 818. As such, in this particular arrangement of lappedworkpieces 808, 806, 818, an exterior outer surface 834 of theadditional steel workpiece 818 now constitutes the steel workpiecesurface 814 that provides the first side 802 of the workpiece stack-up800.

In another example, as shown in FIG. 20, the workpiece stack-up 800 mayinclude the adjacent steel and aluminum workpieces 806, 808 describedabove along with the additional aluminum workpiece 820 that overlaps andis disposed adjacent to the aluminum workpiece 808. When the additionalaluminum workpiece 820 is so positioned, the exterior outer surface 824of the steel workpiece 806 constitutes the steel workpiece surface 814that provides the first side 802 of the workpiece stack-up 800, asbefore, while the aluminum workpiece 808 that lies adjacent to the steelworkpiece 806 now includes a pair of opposed faying surfaces 826, 836.The faying surface 826 of the aluminum workpiece 808 that confronts andcontacts (directly or indirectly) the adjacent faying surface 822 of thesteel workpiece 806 establishes the faying interface 810 between the twoworkpieces 806, 808 as previously described. The other faying surface836 of the aluminum workpiece 808 confronts and makes overlappingcontact (direct or indirect) with a faying surface 838 of the additionalaluminum workpiece 820. As such, in this particular arrangement oflapped workpieces 806, 808, 820, an exterior outer surface 840 of theadditional aluminum workpiece 820 now constitutes the aluminum workpiecesurface 816 that provides the second side 804 of the workpiece stack-up810.

Turning now to FIGS. 21-22, any of the above-described combinations ofthe first welding electrode 200, 300, 420, 620 (collectively referred toby reference numeral 901 with weld face 902) and the second weldingelectrode 220, 320, 520, 720 (collectively referred to by referencenumeral 911 with weld face 912) may be employed to resistance spot weldthe workpiece stack-up 800. The weld face 902 of the first weldingelectrode 901 has the first geometry (dressable by the first cuttingsocket 32 of the cutting tool 10) and the second weld face 912 of thesecond welding electrode 911 has the second geometry (dressable by thesecond cutting socket 34 of the cutting tool 10). The welding electrodes901, 911 are carried on a weld gun (not shown) of any suitable type,including a C-type or an X-type gun, and are electrically coupled to apower supply capable of delivering electrical current—preferably adirect electrical current in the range of 5 kA to 50 kA—between thewelding electrodes 901, 911 and through the workpiece stack-up 800according to a programmed weld schedule. The weld gun may also be fittedwith coolant lines and associated control equipment in order to delivera coolant fluid, such as water, to each of the welding electrodes 901,911 during spot welding operations.

The resistance spot welding method begins by positioning the first andsecond welding electrodes 901, 911 relative to the workpiece stack-up800 such that the first weld face 902 confronts the steel workpiecesurface 814 and the second weld face 912 confronts the aluminumworkpiece surface 816, as shown in FIG. 21. The first weld face 902 andthe second weld face 912 are then pressed against their respective steeland aluminum workpiece surfaces 814, 816 in facial alignment with oneanother under an imposed clamping force at the weld site 812. Theimposed clamping force preferably ranges from 400 lb to 2000 lb or, morenarrowly from 600 lb to 1300 lb. While only the steel and aluminumworkpieces 806, 808 that overlap and lie adjacent to one another,thereby establishing the faying interface 810, are depicted in thisFigure, the following discussion of the resistance spot welding methodapplies equally to instances in which the workpiece stack-up 800includes the additional steel workpiece 818 or the additional aluminumworkpiece 820 (FIGS. 19-20) even though those additional workpieces 318,320 are omitted from the Figures for the sake of clarity.

After the first weld face 902 and the second weld face 912 are pressedagainst the steel and aluminum workpieces surfaces 814, 816 of theworkpiece stack-up 800, respectively, electrical current is passedbetween the welding electrodes 901, 911 by way of their facially alignedweld faces 902, 912. The electrical current exchanged between thewelding electrodes 901, 911 passes through the workpiece stack-up 800and across the faying interface 810 established between the adjacentsteel and aluminum workpieces 806, 808. Resistance to the flow ofelectrical current, which is preferably a DC electrical current having acurrent level that ranges from 5 kA to 50 kA, melts the aluminumworkpiece 808 and creates a molten aluminum weld pool 850 within thealuminum workpiece 808, as shown in FIG. 21. The molten aluminum weldpool 850 wets the faying surface 822 of the steel workpiece 808 andpenetrates a distance into the aluminum workpiece 808 that ranges from20% to 100% of the thickness 8080 of the aluminum workpiece 808 at theweld site 812.

Upon cessation of electrical current flow, the molten aluminum weld pool850 solidifies into a weld joint 852 that weld bonds the steel andaluminum workpieces 806, 808 together at the weld site 812, as shown inFIG. 22, without consuming the faying interface 810 between theworkpiece 806, 808. The weld joint 852 includes resolidified material ofthe aluminum workpiece 808, and may also include one or more reactionlayers of Fe—Al intermetallic compounds adjacent to the faying surface822 of the steel workpiece 806. The one or more Fe—Al intermetalliclayers can include FeAl₃ compounds, Fe₂Al₅ compounds, and possibly otherintermetallic compounds, and typically have a combined total thicknessof 1 μm to 5 μm. The weld joint 852 extends into the aluminum workpiece808 to a distance that often ranges from 20% to 100% (100% being all theway through the aluminum workpiece 808) of the thickness 8080 of thealuminum workpiece 808 at the weld site 812, just like the pre-existingmolten aluminum weld pool 850.

After passage of the electrical current between the welding electrodes901, 911 has ceased and the clamping force imposed by the electrodes901, 911 is no longer needed, the welding electrodes 901, 911 areretracted from their respective steel and aluminum workpieces surfaces814, 816. The resistance spot welding method is then repeated at otherweld sites 812 on the same or a different workpiece stack-up 800. Thecontinued use of the first and second welding electrodes 901, 911 inresistance spot welding operations eventually causes the first weld face902 and the second weld face 912 to become degraded. Such degradation ofthe weld faces 902, 912 is generally unavoidable and at some pointbegins to interfere with the communication of the electrical currentbetween the welding electrodes 901, 911 and through the workpiecestack-up 800. When current flow is interfered with as a result ofappreciable weld face degradation, the formation of the weld joint 852is disrupted, making it difficult to consistently attain good strengthproperties in the joint 852.

The combination of dissimilar materials in the workpiece stack-up 800and the different weld face geometries of the first and second weldingelectrodes 901, 911 leads to different forms of degradation occurring atthe first weld face 902 and the second weld face 912. For instance, thefirst weld face 902 of the first welding electrode 901 may experiencemacro-deformation in the form of mushrooming due to the hightemperatures experienced at the steel workpiece surface 814 and theclamping pressure imposed on the weld face 902, especially when thesteel workpiece 806 includes a high strength steel such as DP, TRIP, orothers. Additionally, the first weld face 902, if constructed from acopper alloy, may react with zinc on the steel workpiece 806, ifpresent, to form a copper-zinc alloy layer on the weld face 902 thataccelerates macro-deformation. The second weld face 912 of the secondwelding electrode 911 on the other hand, if constructed from a copperalloy, may experience a metallurgical reaction between copper andaluminum that forms a copper-aluminum reaction product. Thiscopper-aluminum reaction product can spall and pit the weld face 912.Additionally, the upstanding circular ridges 550 of FIG. 14 may becomedeformed or flattened over time, which compromises the ability of theweld face 524 to communicate electrical current into or out of theworkpiece stack-up 800.

The first weld face 902 and the second weld face 912 may be periodicallydressed by the cutting tool 10 whenever desired to counteract weld facedegradation and thus extend the useful operational liftime of the firstand second welding electrodes 901, 911. Specifically, the first andsecond welding electrodes 901, 911 may be dressed after forming anywherefrom 10 to 100 weld joints 852. That is, the first and second weldingelectrodes 901, 911 may be used to form a first set of weld joints 852,which ranges from 10 to 100, followed by dressing with the cutting tool10. After dressing, the first and second welding electrodes 901, 911 maybe used to form a second set of weld joints 852, which again ranges from10 to 100, followed by another dressing with the cutting tool 10. Foreach welding electrode 901, 911, this pattern of welding and dressingmay continue until the cumulative consumption of weld face materialresulting from the dressing operations renders the electrode 901, 911unfit for continued use. Since each dressing operation with the cuttingtool 10 removes a depth of material ranging from 10 μm to 500 μm, andmore preferably 50 μm to 200 μm, each of the welding electrodes 901, 911can usually withstand anywhere from 10 to 500 dressing operations beforehaving to be replaced with a new electrode of the same weld facegeometry.

Using the cutting tool 10 to dress the first weld face 902 and thesecond weld face 912 can be performed without removing the first andsecond welding electrodes 901, 911 from the weld gun. The dressingoperation involves mounting the cutting tool 10 into a rotatable holder.The first and second welding electrodes 901, 911 are then convergedsimultaneously along the central axis 18 of the through hole 16 of thecutting tool 10 such that the first weld face 902 is received in thefirst cutting socket 32 and the second weld face 912 is received in thesecond cutting socket 34, as illustrated in FIGS. 23-26 for each of theweld face geometry combination previously described with respect toFIGS. 9-17. Such receipt of the weld faces 902, 912 brings them intocontact with the first and second hearing surface(s) 68, 70,respectively, of the one or more cutting flutes 58 of the cutting member14. FIGS. 23-26 illustrate each of the previously described weld facegeometry combinations being received in their respective cutting sockets32, 34 of the cutting tool 10. When the first weld face 902 (204, 304,424, 624) and the second weld face 912 (224, 324, 524, 724) are soreceived, the axis 212, 312, 434, 634 of the first weld face 902 and theaxis 234, 334, 534, 734 of the second weld face 912 are coaxiallyaligned with the central axis 18 of the through hole 16 of the cuttingtool 10.

Upon receipt of the weld faces 902 (204, 304, 424, 624), 912 (224, 324,524, 724) in their respective cutting sockets 32, 34, any upstandingsurface features—namely, the central plateau 232, 332, 432, 632, 732,the plurality of terraces 340, 740, and the upstanding circular ridges550—that may be present are registered with and received in the matchingintrusions defined in the applicable shearing surface(s) 68, 70 of theone or more cutting flutes 58. The cutting tool 10 is then rotated aboutthe central axis 18 of the through hole 16 at a speed that typicallyranges from 100 rpm to 1000 rpm or, more narrowly, from 200 rpm to 500rpm, for a minimum of one to ten or, more narrowly, four to six fullrevolutions about the axes 212, 234, 312, 334, 434, 534, 634, 734 of theweld faces 902 (204, 304, 424, 624), 912 (224, 324, 524, 724). Duringsuch rotation, the leading edges 76, 90 of the shearing surface(s) 68,70 of the one or more cutting flutes 58 are likewise rotated about theaxis 212, 234, 312, 334, 434, 534, 634, 734 of their respective weldfaces 902 (204, 304, 424, 624), 912 (224, 324, 524, 724) while remainingin contact with the weld faces 902 (204, 304, 424, 624), 912 (224, 324,524, 724).

The rotational movement of the leading edges 76, 90 around the weldfaces 902 (204, 304, 424, 624), 912 (224, 324, 524, 724) cuts the firstand second weld faces 902, 912 and their associated transition noses208, 228, 308, 328, 428, 528, 628, 728 to expose fresh weld facematerial and restore the first and second weld face geometries. Anyprior degradation of the weld faces 902 (204, 304, 424, 624), 912 (224,324, 524, 724)—whether it be plastic deformation or reaction materialdeposits (e.g., the result of reactions between cooper/zinc orcopper/aluminum)—is thus virtually eliminated in a single dressingoperation that does not require laborious efforts or significant processdowntime. Once the first weld face 902 (204, 304, 424, 624) and thesecond weld face 912 (224, 324, 524, 724) have been adequately dressed,the welding electrodes 901 (200, 300, 420, 620), 911 (220, 320, 520,720) are retracted from the first and second cutting sockets 32, 34 and,because they are still carried by the weld gun, can be quickly returnedto service.

The above description of preferred exemplary embodiments and specificexamples are merely descriptive in nature; they are not intended tolimit the scope of the claims that follow. Each of the terms used in theappended claims should be given its ordinary and customary meaningunless specifically and unambiguously stated otherwise in thespecification.

The invention claimed is:
 1. A cutting tool capable of dressing a weldface of a first welding electrode so that the weld face of the firstwelding electrode has a first weld face geometry, and dressing a weldface of a second welding electrode so that the weld face of the secondwelding electrode has a second weld face geometry, in which the firstweld face geometry and the second weld face geometry are different fromeach other, the cutting tool comprising: a body having a first end and asecond end that are spaced apart along a central axis of the body, thefirst end of the body having a first opening and the second end of thebody having a second opening; and a cutting member within the body, thecutting member being bisected by an imaginary plane orientedperpendicular to the central axis of the body and the cutting memberhaving a first cutting flute, a second cutting flute, a third cuttingflute, and a fourth cutting flute, each of the first, second, third, andfourth cutting flutes extending inwardly from an interior surface of thebody and comprising a first cutting blade, a second cutting blade, athird cutting blade, and a fourth cutting blade, respectively, with eachof the first cutting blade, the second cutting blade, the third cuttingblade, and the fourth cutting blade having respective first and secondshearing surfaces that are axially spaced apart along the central axisof the body, the first cutting blade, the second cutting blade, thethird cutting blade, and the fourth cutting blade establishing a firstcutting socket and a second cutting socket, the first cutting socketbeing defined by the first shearing surfaces of the cutting blades andbeing accessible through the first opening of the body, and the secondcutting socket being defined by the second shearing surfaces of thecutting blades and being accessible through the second opening of thebody, the first cutting socket being constructed to cut the first weldface geometry into the weld face of the first welding electrode and thesecond cutting socket being constructed to cut the second weld facegeometry into the weld face of the second welding electrode when theweld face of the first welding electrode is received in the firstcutting socket and the weld face of the second welding electrode isreceived in the second cutting socket and the cutting tool is rotatedabout the central axis; wherein the first, second, third, and fourthcutting blades are circumferentially spaced from each other such thateach of the first, second, third, and fourth cutting blades is orientedtransverse to each of its two circumferentially adjacent cutting blades;wherein the respective first shearing surface of each of the first,second, third, and fourth cutting blades comprises, relative to theimaginary plane, a distal convex end portion and a proximal end portionextending inwardly from the distal convex end portion of the respectivefirst shearing surface, the proximal end portion of the respective firstshearing surface of each of the first, second, third, and fourth cuttingblades having corresponding leading and trailing edges relative torotation of the cutting tool about the central axis, wherein theproximal end portion of the respective first shearing surface of each ofthe first, second, third, and fourth cutting blades is inclined at apositive relief angle such that the corresponding leading edge of therespective first shearing surface of each of the first, second, third,and fourth cutting blades is more distal to the imaginary plane than isthe corresponding trailing edge of the respective first shearing surfaceof each of the first, second, third, and fourth cutting blades; whereinthe respective second shearing surface of each of the first, second,third, and fourth cutting blades comprises, relative to the imaginaryplane, a distal convex end portion and a proximal end portion extendinginwardly from the distal convex end portion of the respective secondshearing surface, the proximal end portion of the respective secondshearing surface of each of the first, second, third, and fourth cuttingblades having corresponding leading and trailing edges relative torotation of the cutting tool about the central axis, wherein theproximal end portion of the respective second shearing surface of eachof the first, second, third, and fourth cutting blades is inclined at apositive relief angle such that the corresponding leading edge of therespective second shearing surface of each of the first, second, third,and fourth cutting blades is more distal to the imaginary plane than isthe corresponding trailing edge of the respective second shearingsurface of each of the first, second, third, and fourth cutting blades.2. The cutting tool set forth in claim 1, wherein each of the cuttingflutes comprises a respective elongate foot, and wherein each elongatefoot of the cutting flutes supports the cutting blade of its respectivecutting flute at the interior surface of the body.
 3. The cutting toolset forth in claim 2, wherein the interior surface of the body hasretention channels that extend axially from the first end of the body tothe second end of the body, each of the retention channels being definedby a respective depressed surface of the interior surface of the body,and wherein each elongate foot of the cutting flutes is separatelyfriction fit within one of the retention channels to fixedly retain thecutting member within the body.
 4. The cutting tool set forth in claim2, wherein each elongate foot of the cutting flutes is integrally formedwith the interior surface of the body to fixedly retain the cuttingmember within the body.
 5. The cutting tool set forth in claim 1,wherein the first shearing surface of the first cutting blade and thefirst shearing surface of the third cutting blade are opposed from eachother and separated circumferentially by the first shearing surface ofthe second cutting blade and the first shearing surface of the fourthcutting blade such that each of the first shearing surface of the secondcutting blade and the first shearing surface of the fourth cutting bladeis oriented transverse to the first shearing surface of the firstcutting blade and the first shearing surface of the third cutting blade,each of the leading edge and the trailing edge of the proximal endportion of the first shearing surface of the first cutting blade and theleading edge and the trailing edge of the proximal end portion of thefirst shearing surface of the third cutting blade being profiled so asto extend outwardly from the central axis of the body to the distalconvex end portion of the first shearing surface of the first cuttingblade and the distal convex end portion of the first shearing surface ofthe third cutting blade, respectively, and wherein the second shearingsurface of the second cutting blade and the second shearing surface ofthe fourth cutting blade are opposed from each other and separatedcircumferentially by the second shearing surface of the first cuttingblade and the second shearing surface of the third cutting blade suchthat each of the second shearing surface of the first cutting blade andthe second shearing surface of the third cutting blade is orientedtransverse to the second shearing surface of the second cutting bladeand the second shearing surface of the fourth cutting blade, each of theleading edge and the trailing edge of the proximal end portion of thesecond shearing surface of the second cutting blade and the leading edgeand the trailing edge of the proximal end portion of the second shearingsurface of the fourth cutting blade being profiled so as to extendoutwardly from the central axis of the body to the distal convex endportion of the second shearing surface of the second cutting blade andthe distal convex end portion of the second shearing surface of thefourth cutting blade, respectively.
 6. The cutting tool set forth inclaim 1, wherein the distal convex end portion of each of the firstshearing surface of the first cutting blade, the first shearing surfaceof the second cutting blade, the first shearing surface of the thirdcutting blade, and the first shearing surface of the fourth cuttingblade has corresponding leading and trailing edges relative to rotationof the cutting tool about the central axis, and wherein the distalconvex end portion of the respective first shearing surface of each ofthe first cutting blade, the second cutting blade, the third cuttingblade, and the fourth cutting blade is inclined at a positive reliefangle such that the corresponding leading edge of the distal convex endportion of the respective first shearing surface of each of the firstcutting blade, the second cutting blade, the third cutting blade, andthe fourth cutting blade is more distal to the imaginary plane than isthe corresponding trailing edge of the distal convex end portion of therespective first shearing surface of each of the first cutting blade,the second cutting blade, the third cutting blade, and the fourthcutting blade.
 7. The cutting tool set forth in claim 1, wherein thebody comprises an annular wall having an exterior surface that includesan integral retaining nut, the integral retaining nut having a pluralityof planar surfaces that are arranged around the exterior surface andintersect at circumferentially spaced axial edges.
 8. The cutting toolset forth in claim 7, wherein the body further comprises an integralradial flange that adjoins and bears on an axial end of the integralretaining nut to provide a seating surface that projects transverselyfrom each of the planar surfaces of the integral retaining nut.
 9. Thecutting tool set forth in claim 1, wherein the proximal end portion ofthe respective first shearing surface of each of the first cuttingblade, the second cutting blade, the third cutting blade, and the fourthcutting blade is profiled so that the first weld face geometry that iscut into the weld face of the first welding electrode comprises a planaror domed base weld face surface that has a diameter between 3 mm and 16mm, and wherein the proximal end portion of the respective secondshearing surface of each of the first cutting blade, the second cuttingblade, the third cutting blade, and the fourth cutting blade is profiledso that the second weld face geometry that is cut into the weld face ofthe second welding electrode comprises a domed base weld face surfacethat has a diameter between 8 mm and 20 mm and further includes acentral plateau centered on the domed base weld face surface of the weldface of the second welding electrode along with a plurality of terracesthat surround the central plateau.
 10. The cutting tool set forth inclaim 1, wherein the proximal end portion of the respective firstshearing surface of each of the first cutting blade, the second cuttingblade, the third cutting blade, and the fourth cutting blade is profiledso that the first weld face geometry that is cut into the weld face ofthe first welding electrode comprises a domed base weld face surfacethat has a diameter between 8 mm and 20 mm and further includes acentral plateau centered on the domed base weld face surface of the weldface of the first welding electrode, and wherein the proximal endportion of the respective second shearing surface of each of the firstcutting blade, the second cutting blade, the third cutting blade, andthe fourth cutting blade is profiled so that the second weld facegeometry that is cut into the weld face of the second welding electrodecomprises a domed base weld face surface that has a diameter between 8mm and 20 mm and a series of upstanding circular ridges that projectoutwardly from the domed base weld face surface of the weld face of thesecond welding electrode.
 11. The cutting tool set forth in claim 10,wherein the series of upstanding circular ridges includes anywhere fromtwo to ten upstanding circular ridges that increase in diameter from aninnermost upstanding circular ridge to an outermost upstanding circularridge, the upstanding circular ridges being spaced apart on the domedbase weld face surface of the weld face of the second welding electrodeby a distance of 50 μm to 1800 μm, and each of the upstanding circularridges having a ridge height that ranges from 20 μm to 500 μm.
 12. Thecutting tool set forth in claim 1, wherein the proximal end portion ofthe respective first shearing surface of each of the first cuttingblade, the second cutting blade, the third cutting blade, and the fourthcutting blade is profiled so that the first weld face geometry that iscut into the weld face of the first welding electrode comprises a domedbase weld face surface that has a diameter between 8 mm and 20 mm andfurther includes a central plateau centered on the domed base weld facesurface of the weld face of the first welding electrode, and wherein theproximal end portion of the respective second shearing surface of eachof the first cutting blade, the second cutting blade, the third cuttingblade, and the fourth cutting blade is profiled so that the second weldface geometry that is cut into the weld face of the second weldingelectrode comprises a domed base weld face surface that has a diameterbetween 8 mm and 20 mm and further includes a central plateau centeredon the domed base weld face surface of the weld face of the secondwelding electrode along with a plurality of terraces that surround thecentral plateau of the weld face of the second welding electrode. 13.The cutting tool set forth in claim 1, wherein the proximal end portionof the respective first shearing surface of each of the first cuttingblade, the second cutting blade, the third cutting blade, and the fourthcutting blade is profiled so that the first weld face geometry that iscut into the weld face of the first welding electrode comprises a planaror domed base weld face surface that has a diameter between 3 mm and 16mm, and wherein the proximal end portion of the respective secondshearing surface of each of the first cutting blade, the second cuttingblade, the third cutting blade, and the fourth cutting blade is profiledso that the second weld face geometry that is cut into the weld face ofthe second welding electrode comprises a domed base weld face surfacethat has a diameter between 8 mm and 20 mm and further includes acentral plateau centered on the domed base weld face surface of the weldface of the second welding electrode.
 14. A cutting tool capable ofdressing a weld face of a first welding electrode so that the weld faceof the first welding electrode has a first weld face geometry, anddressing a weld face of a second welding electrode so that the weld faceof the second welding electrode has a second weld face geometry, inwhich the first weld face geometry and the second weld face geometry aredifferent from each other, the cutting tool comprising: a body thatextends longitudinally along a central axis between a first end and asecond end, and a cutting member within the body, the cutting memberestablishing a first cutting socket accessible through a first openingat the first end of the body and a second cutting socket accessiblethrough a second opening at the second end of the body, the cuttingmember comprising a first cutting flute that includes a first cuttingblade having first and second shearing surfaces that are axially spacedapart along the central axis of the body and that define, at least inpart, the first and second cutting sockets, respectively, wherein animaginary plane oriented perpendicular to the central axis bisects thecutting member, wherein the first shearing surface of the first cuttingblade comprises a distal convex end portion and a proximal end portionrelative to the imaginary plane, the proximal end portion of the firstshearing surface of the first cutting blade extending radially inwardfrom the distal convex end portion of the first shearing surface andbeing profiled to cut the first weld face geometry into the weld face ofthe first welding electrode, and wherein the second shearing surface ofthe first cutting blade comprises a distal convex end portion and aproximal end portion relative to the imaginary plane, the proximal endportion of the second shearing surface of the first cutting bladeextending radially inward from the distal convex end portion of thesecond shearing surface and being profiled to cut the second weld facegeometry into the weld face of the second welding electrode; wherein theproximal end portion of the first shearing surface of the first cuttingblade is profiled so that the first weld face geometry that is cut intothe weld face of the first welding electrode by the proximal end portionof the first shearing surface of the first cutting blade comprises aplanar or domed base weld face surface that has a diameter between 3 mmand 16 mm, and wherein the proximal end portion of the second shearingsurface of the first cutting blade is profiled so that the second weldface geometry that is cut into the weld face of the second weldingelectrode by the proximal end portion of the second shearing surface ofthe first cutting blade comprises a domed base weld face surface thathas a diameter between 8 mm and 20 mm and further includes a centralplateau centered on the domed base weld face surface of the weld face ofthe second welding electrode.
 15. The cutting tool set forth in claim14, wherein the cutting member further comprises a second cutting flutehaving a second cutting blade, a third cutting flute having a thirdcutting blade, and a fourth cutting flute having a fourth cutting blade,the first, second, third, and fourth cutting blades beingcircumferentially spaced from each other such that each of the first,second, third, and fourth cutting blades is oriented transverse to eachof its two circumferentially adjacent cutting blades; wherein each ofthe second cutting blade, the third cutting blade, and the fourthcutting blade includes respective first and second shearing surfacesthat are axially spaced apart along the central axis of the body;wherein the respective first shearing surface of each of the secondcutting blade, the third cutting blade, and the fourth cutting bladecomprises a distal convex end portion and a proximal end portionrelative to the imaginary plane, the proximal end portion of each of thefirst shearing surface of the second cutting blade, the first shearingsurface of the third cutting blade, and the first shearing surface ofthe fourth cutting blade extending radially inwardly from the distalconvex end portion of the first shearing surface of the second cuttingblade, the distal convex end portion of first shearing surface of thethird cutting blade, and the distal convex end portion of first shearingsurface of the fourth cutting blade, respectively, wherein the firstshearing surface of the second cutting blade, the first shearing surfaceof the third cutting blade, and the first shearing surface of the fourthcutting blade define the first cutting socket along with the firstshearing surface of the first cutting blade; wherein the respectivesecond shearing surface of each of the second cutting blade, the thirdcutting blade, and the fourth cutting blade comprises a distal convexend portion and a proximal end portion relative to the imaginary plane,the proximal end portion of each of the second shearing surface of thesecond cutting blade, the second shearing surface of the third cuttingblade, and the second shearing surface of the fourth cutting bladeextending radially inwardly from the distal convex end portion of thesecond shearing surface of the second cutting blade, the distal convexend portion of second shearing surface of the third cutting blade, andthe distal convex end portion of second shearing surface of the fourthcutting blade, respectively, wherein the second shearing surface of thesecond cutting blade, the second shearing surface of the third cuttingblade, and the second shearing surface of the fourth cutting bladedefine the second cutting socket along with the second shearing surfaceof the first cutting blade.
 16. The cutting tool set forth in claim 15,wherein the first shearing surface of the first cutting blade and thefirst shearing surface of the third cutting blade are opposed from eachother and separated circumferentially by the first shearing surface ofthe second cutting blade and the first shearing surface of the fourthcutting blade such that each of the first shearing surface of the secondcutting blade and the first shearing surface of the fourth cutting bladeis oriented transverse to the first shearing surface of the firstcutting blade and the first shearing surface of the third cutting blade;each of the proximal end portion of the first shearing surface of thefirst cutting blade and the proximal end portion of the first shearingsurface of the third cutting blade having corresponding leading andtrailing edges relative to rotation of the cutting tool about thecentral axis, the proximal end portion of each of the first shearingsurface of the first cutting blade and the first shearing surface of thethird cutting blade being inclined relative to the imaginary plane fromthe corresponding leading edge to the corresponding trailing edge and,further, the leading edge and the trailing edge of the proximal endportion of each of the first shearing surface of the first cutting bladeand the first shearing surface of the third cutting blade being profiledso as to extend outwardly as the corresponding leading and trailingedges of the proximal end portion of each of the first shearing surfaceof the first cutting blade and the first shearing surface of the thirdcutting blade progress towards the distal convex end portion of thefirst shearing surface of the first cutting blade and the distal convexend portion of the first shearing surface of the third cutting blade,respectively; wherein the second shearing surface of the second cuttingblade and the second shearing surface of the fourth cutting blade areopposed from each other and separated circumferentially by the secondshearing surface of the first cutting blade and the second shearingsurface of the third cutting blade such that each of the second shearingsurface of the first cutting blade and the second shearing surface ofthe third cutting blade is oriented transverse to the second shearingsurface of the second cutting blade and the second shearing surface ofthe fourth cutting blade; each of the proximal end portion of the secondshearing surface of the second cutting blade and the proximal endportion of the second shearing surface of the fourth cutting bladehaving corresponding leading and trailing edges relative to rotation ofthe cutting tool about the central axis, the proximal end portion ofeach of the second shearing surface of the second cutting blade and thesecond shearing surface of the fourth cutting blade being inclinedrelative to the imaginary plane from the corresponding leading edge tothe corresponding trailing edge and, further, the leading edge and thetrailing edge of the proximal end portion of each of the second shearingsurface of the second cutting blade and the second shearing surface ofthe fourth cutting blade being profiled so as to extend outwardly as thecorresponding leading and trailing edges of the proximal end portion ofeach of the second shearing surface second cutting blade and the secondshearing surface of the fourth cutting blade progress towards the distalconvex end portion of the second shearing surface of the second cuttingblade and the distal convex end portion of the second shearing surfaceof the fourth cutting blade, respectively.
 17. A cutting toolcomprising: a body that extends longitudinally along a central axisbetween a first end and a second end, and a cutting member within thebody, the cutting member being bisected by an imaginary plane orientedperpendicular to the central axis and further establishing (i) a firstcutting socket accessible through a first opening at the first end ofthe body and (ii) a second cutting socket accessible through a secondopening at the second end of the body, the cutting member comprising afirst cutting flute, a second cutting flute, a third cutting flute, anda fourth cutting flute that are circumferentially spaced from each otherwithin the body of the cutting tool, each of the first cutting flute,the second cutting flute, the third cutting flute, and the fourthcutting flute comprising: a respective cutting blade; and a respectiveelongate foot that supports the corresponding cutting blade at aninterior surface of the body, wherein the interior surface of the bodyhas retention channels that extend axially from the first end of thebody to the second end of the body, each of the retention channels beingdefined by a depressed surface of the interior surface of the body, andwherein the elongate foot of each of the first cutting flute, the secondcutting flute, the third cutting flute, and the fourth cutting flute isseparately friction fit within one of the retention channels to fixedlyretain the cutting member within the body; wherein each of the cuttingblades includes respective first and second shearing surfaces that areaxially spaced apart along the central axis of the body and that define,at least in part, the first and second cutting sockets, respectively,wherein each of the first shearing surfaces comprises a respectivedistal convex end portion and a respective proximal end portion relativeto the imaginary plane, each of the distal convex end portions of thefirst shearing surfaces extending radially inward from the respectiveelongate foot proximate the first end of the body, and each of theproximal end portions of the first shearing surfaces extending radiallyinward from the respective distal convex end portion of the respectivefirst shearing surface and away from a plane of the first opening of thebody, and wherein each of the second shearing surfaces comprises arespective distal convex end portion and a respective proximal endportion relative to the imaginary plane, each of the distal convex endportions of the second shearing surfaces extending radially inward fromthe respective elongate foot proximate the second end of the body, andeach of the proximal end portions of the second shearing surfacesextending radially inward from the respective distal convex end portionof the respective second shearing surface and away from a plane of thesecond opening of the body; wherein the proximal end portion of thefirst shearing surface of the cutting blade of each of the first cuttingflute, the second cutting flute, the third cutting flute, and the fourthcutting flute is profiled to achieve by cutting, upon rotation of thecutting tool about the central axis of the body, a first weld facegeometry; wherein the proximal end portion of the second shearingsurface of the cutting blade of each of the first cutting flute, thesecond cutting flute, the third cutting flute, and the fourth cuttingflute is profiled to achieve by cutting, upon rotation of the cuttingtool about the central axis of the body, a second weld face geometry.